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 $192.65   7.512%   $207.1219   $207.12   $207.10   $207.10  
  Purchase #2 $43.93   3.827%   $45.6112   $45.61   $45.60   $45.60  
  Purchase #3 $212.61   7.494%   $228.543   $228.54   $228.55   $228.50  
  Purchase #4 $151.55   3.278%   $156.5178   $156.52   $156.50   $156.50  
  Purchase #5 $197.68   8.813%   $215.1015   $215.10   $215.10   $215.10  
  Purchase #6 $186.41   4.490%   $194.7798   $194.78   $194.80   $194.80  
  Purchase #7 $134.41   12.438%   $151.1279   $151.13   $151.15   $151.10  
  7 purchase totals = $1,119.24       $1,198.8031   $1,198.80   $1,198.80   $1,198.70