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 $61.91   5.343%   $65.2179   $65.22   $65.20   $65.20  
  Purchase #2 $194.78   12.737%   $219.5891   $219.59   $219.60   $219.60  
  Purchase #3 $179.93   10.418%   $198.6751   $198.68   $198.70   $198.70  
  Purchase #4 $68.59   6.123%   $72.7898   $72.79   $72.80   $72.80  
  Purchase #5 $39.86   5.120%   $41.9008   $41.90   $41.90   $41.90  
  Purchase #6 $207.38   5.172%   $218.1057   $218.11   $218.10   $218.10  
  Purchase #7 $239.39   3.251%   $247.1726   $247.17   $247.15   $247.20  
  7 purchase totals = $991.84       $1,063.4510   $1,063.46   $1,063.45   $1,063.50