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 $202.49   11.741%   $226.2644   $226.26   $226.25   $226.30  
  Purchase #2 $33.48   13.563%   $38.0209   $38.02   $38.00   $38.00  
  Purchase #3 $68.70   10.580%   $75.9685   $75.97   $75.95   $76.00  
  Purchase #4 $232.31   6.606%   $247.6564   $247.66   $247.65   $247.70  
  Purchase #5 $191.69   6.640%   $204.4182   $204.42   $204.40   $204.40  
  Purchase #6 $59.47   8.494%   $64.5214   $64.52   $64.50   $64.50  
  Purchase #7 $237.27   6.570%   $252.8586   $252.86   $252.85   $252.90  
  7 purchase totals = $1,025.41       $1,109.7084   $1,109.71   $1,109.60   $1,109.80