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 $236.43   11.603%   $263.863   $263.86   $263.85   $263.90  
  Purchase #2 $203.58   12.319%   $228.659   $228.66   $228.65   $228.70  
  Purchase #3 $214.96   8.579%   $233.4014   $233.40   $233.40   $233.40  
  Purchase #4 $69.26   9.148%   $75.5959   $75.60   $75.60   $75.60  
  Purchase #5 $108.53   10.840%   $120.2947   $120.29   $120.30   $120.30  
  Purchase #6 $185.76   9.238%   $202.9205   $202.92   $202.90   $202.90  
  Purchase #7 $187.96   8.543%   $204.0174   $204.02   $204.00   $204.00  
  7 purchase totals = $1,206.48       $1,328.7519   $1,328.75   $1,328.70   $1,328.80