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 $188.94   7.523%   $203.154   $203.15   $203.15   $203.20  
  Purchase #2 $60.87   4.144%   $63.3925   $63.39   $63.40   $63.40  
  Purchase #3 $176.88   13.572%   $200.8862   $200.89   $200.90   $200.90  
  Purchase #4 $166.89   3.807%   $173.2435   $173.24   $173.25   $173.20  
  Purchase #5 $176.52   12.554%   $198.6803   $198.68   $198.70   $198.70  
  Purchase #6 $240.71   6.679%   $256.787   $256.79   $256.80   $256.80  
  Purchase #7 $75.75   4.325%   $79.0262   $79.03   $79.05   $79.00  
  7 purchase totals = $1,086.56       $1,175.1697   $1,175.17   $1,175.25   $1,175.20