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 $54.77   8.565%   $59.4611   $59.46   $59.45   $59.50  
  Purchase #2 $213.95   7.345%   $229.6646   $229.66   $229.65   $229.70  
  Purchase #3 $26.69   9.200%   $29.1455   $29.15   $29.15   $29.10  
  Purchase #4 $221.34   4.586%   $231.4907   $231.49   $231.50   $231.50  
  Purchase #5 $155.25   8.444%   $168.3593   $168.36   $168.35   $168.40  
  Purchase #6 $110.77   12.182%   $124.264   $124.26   $124.25   $124.30  
  Purchase #7 $184.64   9.852%   $202.8307   $202.83   $202.85   $202.80  
  7 purchase totals = $967.41       $1,045.2159   $1,045.21   $1,045.20   $1,045.30