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 $70.87   8.512%   $76.9025   $76.90   $76.90   $76.90  
  Purchase #2 $244.53   9.621%   $268.0562   $268.06   $268.05   $268.10  
  Purchase #3 $212.84   5.187%   $223.88   $223.88   $223.90   $223.90  
  Purchase #4 $121.82   6.733%   $130.0221   $130.02   $130.00   $130.00  
  Purchase #5 $157.99   5.823%   $167.1898   $167.19   $167.20   $167.20  
  Purchase #6 $200.50   11.710%   $223.9786   $223.98   $224.00   $224.00  
  Purchase #7 $85.42   6.520%   $90.9894   $90.99   $91.00   $91.00  
  7 purchase totals = $1,093.97       $1,181.0186   $1,181.02   $1,181.05   $1,181.10