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 $141.46   5.572%   $149.3422   $149.34   $149.35   $149.30  
  Purchase #2 $243.36   7.798%   $262.3372   $262.34   $262.35   $262.30  
  Purchase #3 $84.92   12.625%   $95.6412   $95.64   $95.65   $95.60  
  Purchase #4 $65.60   12.544%   $73.8289   $73.83   $73.85   $73.80  
  Purchase #5 $230.74   9.766%   $253.2741   $253.27   $253.25   $253.30  
  Purchase #6 $105.89   11.844%   $118.4316   $118.43   $118.45   $118.40  
  Purchase #7 $58.81   4.569%   $61.497   $61.50   $61.50   $61.50  
  7 purchase totals = $930.78       $1,014.3522   $1,014.35   $1,014.40   $1,014.20