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 $197.29   4.424%   $206.0181   $206.02   $206.00   $206.00  
  Purchase #2 $123.72   9.292%   $135.2161   $135.22   $135.20   $135.20  
  Purchase #3 $10.28   7.463%   $11.0472   $11.05   $11.05   $11.00  
  Purchase #4 $241.49   11.398%   $269.015   $269.02   $269.00   $269.00  
  Purchase #5 $39.64   5.368%   $41.7679   $41.77   $41.75   $41.80  
  Purchase #6 $52.40   12.833%   $59.1245   $59.12   $59.10   $59.10  
  Purchase #7 $31.68   4.266%   $33.0315   $33.03   $33.05   $33.00  
  7 purchase totals = $696.50       $755.2203   $755.23   $755.15   $755.10