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 $226.47   12.167%   $254.0246   $254.02   $254.00   $254.00  
  Purchase #2 $220.29   4.538%   $230.2868   $230.29   $230.30   $230.30  
  Purchase #3 $216.59   6.303%   $230.2417   $230.24   $230.25   $230.20  
  Purchase #4 $79.52   10.140%   $87.5833   $87.58   $87.60   $87.60  
  Purchase #5 $177.93   3.756%   $184.6131   $184.61   $184.60   $184.60  
  Purchase #6 $204.80   10.220%   $225.7306   $225.73   $225.75   $225.70  
  Purchase #7 $226.74   9.443%   $248.1511   $248.15   $248.15   $248.20  
  7 purchase totals = $1,352.34       $1,460.6312   $1,460.62   $1,460.65   $1,460.60