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 $87.78   9.779%   $96.364   $96.36   $96.35   $96.40  
  Purchase #2 $249.26   9.757%   $273.5803   $273.58   $273.60   $273.60  
  Purchase #3 $87.49   9.483%   $95.7867   $95.79   $95.80   $95.80  
  Purchase #4 $184.48   5.335%   $194.322   $194.32   $194.30   $194.30  
  Purchase #5 $80.93   13.700%   $92.0174   $92.02   $92.00   $92.00  
  Purchase #6 $130.57   11.110%   $145.0763   $145.08   $145.10   $145.10  
  Purchase #7 $51.32   10.171%   $56.5398   $56.54   $56.55   $56.50  
  7 purchase totals = $871.83       $953.6865   $953.69   $953.70   $953.70