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 $85.74   11.672%   $95.7476   $95.75   $95.75   $95.70  
  Purchase #2 $128.36   12.172%   $143.984   $143.98   $144.00   $144.00  
  Purchase #3 $108.74   3.199%   $112.2186   $112.22   $112.20   $112.20  
  Purchase #4 $248.65   4.240%   $259.1928   $259.19   $259.20   $259.20  
  Purchase #5 $243.82   3.490%   $252.3293   $252.33   $252.35   $252.30  
  Purchase #6 $157.31   8.297%   $170.362   $170.36   $170.35   $170.40  
  Purchase #7 $191.60   5.855%   $202.8182   $202.82   $202.80   $202.80  
  7 purchase totals = $1,164.22       $1,236.6525   $1,236.65   $1,236.65   $1,236.60