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 $168.77   9.171%   $184.2479   $184.25   $184.25   $184.20  
  Purchase #2 $85.55   9.346%   $93.5455   $93.55   $93.55   $93.50  
  Purchase #3 $228.80   9.802%   $251.227   $251.23   $251.25   $251.20  
  Purchase #4 $238.57   8.595%   $259.0751   $259.08   $259.10   $259.10  
  Purchase #5 $233.27   9.153%   $254.6212   $254.62   $254.60   $254.60  
  Purchase #6 $221.40   9.419%   $242.2537   $242.25   $242.25   $242.30  
  Purchase #7 $58.60   3.717%   $60.7782   $60.78   $60.80   $60.80  
  7 purchase totals = $1,234.96       $1,345.7486   $1,345.76   $1,345.80   $1,345.70