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 $204.58   10.456%   $225.9709   $225.97   $225.95   $226.00  
  Purchase #2 $219.98   10.670%   $243.4519   $243.45   $243.45   $243.50  
  Purchase #3 $10.67   7.500%   $11.4703   $11.47   $11.45   $11.50  
  Purchase #4 $6.59   9.309%   $7.2035   $7.20   $7.20   $7.20  
  Purchase #5 $33.52   10.278%   $36.9652   $36.97   $36.95   $37.00  
  Purchase #6 $209.48   10.579%   $231.6409   $231.64   $231.65   $231.60  
  Purchase #7 $23.45   9.838%   $25.757   $25.76   $25.75   $25.80  
  7 purchase totals = $708.27       $782.4597   $782.46   $782.40   $782.60