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 $87.96   7.136%   $94.2368   $94.24   $94.25   $94.20  
  Purchase #2 $171.28   3.162%   $176.6959   $176.70   $176.70   $176.70  
  Purchase #3 $33.99   3.740%   $35.2612   $35.26   $35.25   $35.30  
  Purchase #4 $106.70   11.374%   $118.8361   $118.84   $118.85   $118.80  
  Purchase #5 $238.96   3.338%   $246.9365   $246.94   $246.95   $246.90  
  Purchase #6 $243.48   8.587%   $264.3876   $264.39   $264.40   $264.40  
  Purchase #7 $242.48   11.630%   $270.6804   $270.68   $270.70   $270.70  
  7 purchase totals = $1,124.85       $1,207.0345   $1,207.05   $1,207.10   $1,207.00