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 $58.35   3.530%   $60.4098   $60.41   $60.40   $60.40  
  Purchase #2 $72.97   12.307%   $81.9504   $81.95   $81.95   $82.00  
  Purchase #3 $224.39   12.201%   $251.7678   $251.77   $251.75   $251.80  
  Purchase #4 $107.94   11.561%   $120.4189   $120.42   $120.40   $120.40  
  Purchase #5 $85.75   8.104%   $92.6992   $92.70   $92.70   $92.70  
  Purchase #6 $240.40   12.564%   $270.6039   $270.60   $270.60   $270.60  
  Purchase #7 $192.59   12.753%   $217.151   $217.15   $217.15   $217.20  
  7 purchase totals = $982.39       $1,095.0010   $1,095.00   $1,094.95   $1,095.10