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 $205.52   4.132%   $214.0121   $214.01   $214.00   $214.00  
  Purchase #2 $147.59   10.138%   $162.5527   $162.55   $162.55   $162.60  
  Purchase #3 $168.70   7.835%   $181.9176   $181.92   $181.90   $181.90  
  Purchase #4 $46.58   5.267%   $49.0334   $49.03   $49.05   $49.00  
  Purchase #5 $68.95   9.869%   $75.7547   $75.75   $75.75   $75.80  
  Purchase #6 $140.59   10.622%   $155.5235   $155.52   $155.50   $155.50  
  Purchase #7 $166.63   10.568%   $184.2395   $184.24   $184.25   $184.20  
  7 purchase totals = $944.56       $1,023.0335   $1,023.02   $1,023.00   $1,023.00