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 $118.30   6.528%   $126.0226   $126.02   $126.00   $126.00  
  Purchase #2 $214.65   5.373%   $226.1831   $226.18   $226.20   $226.20  
  Purchase #3 $186.67   8.767%   $203.0354   $203.04   $203.05   $203.00  
  Purchase #4 $138.73   4.353%   $144.7689   $144.77   $144.75   $144.80  
  Purchase #5 $197.61   7.378%   $212.1897   $212.19   $212.20   $212.20  
  Purchase #6 $53.52   13.669%   $60.8356   $60.84   $60.85   $60.80  
  Purchase #7 $37.40   11.466%   $41.6883   $41.69   $41.70   $41.70  
  7 purchase totals = $946.88       $1,014.7236   $1,014.73   $1,014.75   $1,014.70