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 $214.79   13.738%   $244.2979   $244.30   $244.30   $244.30  
  Purchase #2 $129.52   8.868%   $141.0058   $141.01   $141.00   $141.00  
  Purchase #3 $118.84   5.563%   $125.4511   $125.45   $125.45   $125.50  
  Purchase #4 $113.33   6.214%   $120.3723   $120.37   $120.35   $120.40  
  Purchase #5 $212.55   8.533%   $230.6869   $230.69   $230.70   $230.70  
  Purchase #6 $56.47   9.158%   $61.6415   $61.64   $61.65   $61.60  
  Purchase #7 $109.75   11.363%   $122.2209   $122.22   $122.20   $122.20  
  7 purchase totals = $955.25       $1,045.6764   $1,045.68   $1,045.65   $1,045.70