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 $71.58   3.300%   $73.9421   $73.94   $73.95   $73.90  
  Purchase #2 $201.38   5.163%   $211.7772   $211.78   $211.80   $211.80  
  Purchase #3 $41.32   9.198%   $45.1206   $45.12   $45.10   $45.10  
  Purchase #4 $187.60   12.561%   $211.1644   $211.16   $211.15   $211.20  
  Purchase #5 $178.47   12.353%   $200.5164   $200.52   $200.50   $200.50  
  Purchase #6 $79.69   5.122%   $83.7717   $83.77   $83.75   $83.80  
  Purchase #7 $176.48   4.682%   $184.7428   $184.74   $184.75   $184.70  
  7 purchase totals = $936.52       $1,011.0352   $1,011.03   $1,011.00   $1,011.00