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 $62.52   10.723%   $69.224   $69.22   $69.20   $69.20  
  Purchase #2 $248.36   7.788%   $267.7023   $267.70   $267.70   $267.70  
  Purchase #3 $150.74   11.766%   $168.4761   $168.48   $168.50   $168.50  
  Purchase #4 $181.95   8.514%   $197.4412   $197.44   $197.45   $197.40  
  Purchase #5 $219.86   5.543%   $232.0468   $232.05   $232.05   $232.00  
  Purchase #6 $171.34   6.570%   $182.597   $182.60   $182.60   $182.60  
  Purchase #7 $26.34   7.642%   $28.3529   $28.35   $28.35   $28.40  
  7 purchase totals = $1,061.11       $1,145.8403   $1,145.84   $1,145.85   $1,145.80