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 $95.72   7.841%   $103.2254   $103.23   $103.25   $103.20  
  Purchase #2 $243.27   9.419%   $266.1836   $266.18   $266.20   $266.20  
  Purchase #3 $102.85   3.563%   $106.5145   $106.51   $106.50   $106.50  
  Purchase #4 $44.49   9.446%   $48.6925   $48.69   $48.70   $48.70  
  Purchase #5 $101.85   4.588%   $106.5229   $106.52   $106.50   $106.50  
  Purchase #6 $246.26   9.456%   $269.5463   $269.55   $269.55   $269.50  
  Purchase #7 $162.97   7.580%   $175.3231   $175.32   $175.30   $175.30  
  7 purchase totals = $997.41       $1,076.0083   $1,076.00   $1,076.00   $1,075.90