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 $206.89   13.146%   $234.0878   $234.09   $234.10   $234.10  
  Purchase #2 $238.44   6.240%   $253.3187   $253.32   $253.30   $253.30  
  Purchase #3 $87.80   9.287%   $95.954   $95.95   $95.95   $96.00  
  Purchase #4 $83.88   4.536%   $87.6848   $87.68   $87.70   $87.70  
  Purchase #5 $181.47   7.263%   $194.6502   $194.65   $194.65   $194.70  
  Purchase #6 $243.78   3.796%   $253.0339   $253.03   $253.05   $253.00  
  Purchase #7 $34.92   3.194%   $36.0353   $36.04   $36.05   $36.00  
  7 purchase totals = $1,077.18       $1,154.7647   $1,154.76   $1,154.80   $1,154.80