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 $85.75   11.731%   $95.8093   $95.81   $95.80   $95.80  
  Purchase #2 $207.95   5.339%   $219.0525   $219.05   $219.05   $219.10  
  Purchase #3 $149.63   12.831%   $168.829   $168.83   $168.85   $168.80  
  Purchase #4 $62.35   12.292%   $70.0141   $70.01   $70.00   $70.00  
  Purchase #5 $132.95   5.435%   $140.1758   $140.18   $140.20   $140.20  
  Purchase #6 $115.74   13.282%   $131.1126   $131.11   $131.10   $131.10  
  Purchase #7 $202.58   3.692%   $210.0593   $210.06   $210.05   $210.10  
  7 purchase totals = $956.95       $1,035.0526   $1,035.05   $1,035.05   $1,035.10