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 $41.74   4.364%   $43.5615   $43.56   $43.55   $43.60  
  Purchase #2 $197.97   9.573%   $216.9217   $216.92   $216.90   $216.90  
  Purchase #3 $101.25   7.511%   $108.8549   $108.85   $108.85   $108.90  
  Purchase #4 $170.78   8.173%   $184.7378   $184.74   $184.75   $184.70  
  Purchase #5 $124.52   3.771%   $129.2156   $129.22   $129.20   $129.20  
  Purchase #6 $171.28   12.197%   $192.171   $192.17   $192.15   $192.20  
  Purchase #7 $62.82   11.718%   $70.1812   $70.18   $70.20   $70.20  
  7 purchase totals = $870.36       $945.6437   $945.64   $945.60   $945.70