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 $91.36   4.707%   $95.6603   $95.66   $95.65   $95.70  
  Purchase #2 $169.31   9.158%   $184.8154   $184.82   $184.80   $184.80  
  Purchase #3 $154.48   11.766%   $172.6561   $172.66   $172.65   $172.70  
  Purchase #4 $38.52   4.125%   $40.109   $40.11   $40.10   $40.10  
  Purchase #5 $232.35   10.440%   $256.6073   $256.61   $256.60   $256.60  
  Purchase #6 $96.43   6.518%   $102.7153   $102.72   $102.70   $102.70  
  Purchase #7 $161.90   8.158%   $175.1078   $175.11   $175.10   $175.10  
  7 purchase totals = $944.35       $1,027.6712   $1,027.69   $1,027.60   $1,027.70