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 $233.70   13.635%   $265.565   $265.57   $265.55   $265.60  
  Purchase #2 $246.35   11.142%   $273.7983   $273.80   $273.80   $273.80  
  Purchase #3 $244.68   7.580%   $263.2267   $263.23   $263.25   $263.20  
  Purchase #4 $68.58   6.667%   $73.1522   $73.15   $73.15   $73.20  
  Purchase #5 $206.44   6.868%   $220.6183   $220.62   $220.60   $220.60  
  Purchase #6 $243.84   7.493%   $262.1109   $262.11   $262.10   $262.10  
  Purchase #7 $219.90   3.703%   $228.0429   $228.04   $228.05   $228.00  
  7 purchase totals = $1,463.49       $1,586.5143   $1,586.52   $1,586.50   $1,586.50