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 $86.50   9.406%   $94.6362   $94.64   $94.65   $94.60  
  Purchase #2 $244.52   9.583%   $267.9524   $267.95   $267.95   $268.00  
  Purchase #3 $88.45   7.646%   $95.2129   $95.21   $95.20   $95.20  
  Purchase #4 $181.56   8.712%   $197.3775   $197.38   $197.40   $197.40  
  Purchase #5 $192.96   11.284%   $214.7336   $214.73   $214.75   $214.70  
  Purchase #6 $41.47   10.524%   $45.8343   $45.83   $45.85   $45.80  
  Purchase #7 $120.48   6.700%   $128.5522   $128.55   $128.55   $128.60  
  7 purchase totals = $955.94       $1,044.2991   $1,044.29   $1,044.35   $1,044.30