Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $195.87   3.730%   $203.176   $203.18   $203.20   $203.20  
  Purchase #2 $120.40   9.279%   $131.5719   $131.57   $131.55   $131.60  
  Purchase #3 $148.62   12.110%   $166.6179   $166.62   $166.60   $166.60  
  Purchase #4 $149.57   9.309%   $163.4935   $163.49   $163.50   $163.50  
  Purchase #5 $206.76   12.793%   $233.2108   $233.21   $233.20   $233.20  
  Purchase #6 $243.53   8.261%   $263.648   $263.65   $263.65   $263.60  
  Purchase #7 $195.98   3.294%   $202.4356   $202.44   $202.45   $202.40  
  7 purchase totals = $1,260.73       $1,364.1537   $1,364.16   $1,364.15   $1,364.10