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 $88.48   8.325%   $95.846   $95.85   $95.85   $95.80  
  Purchase #2 $131.96   13.620%   $149.933   $149.93   $149.95   $149.90  
  Purchase #3 $156.41   9.200%   $170.7997   $170.80   $170.80   $170.80  
  Purchase #4 $34.96   9.235%   $38.1886   $38.19   $38.20   $38.20  
  Purchase #5 $216.50   12.426%   $243.4023   $243.40   $243.40   $243.40  
  Purchase #6 $195.94   6.248%   $208.1823   $208.18   $208.20   $208.20  
  Purchase #7 $124.49   4.726%   $130.3734   $130.37   $130.35   $130.40  
  7 purchase totals = $948.74       $1,036.7253   $1,036.72   $1,036.75   $1,036.70