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 $67.58   13.668%   $76.8168   $76.82   $76.80   $76.80  
  Purchase #2 $151.62   7.405%   $162.8475   $162.85   $162.85   $162.80  
  Purchase #3 $59.82   11.162%   $66.4971   $66.50   $66.50   $66.50  
  Purchase #4 $12.64   11.416%   $14.083   $14.08   $14.10   $14.10  
  Purchase #5 $243.74   9.685%   $267.3462   $267.35   $267.35   $267.30  
  Purchase #6 $223.31   4.475%   $233.3031   $233.30   $233.30   $233.30  
  Purchase #7 $207.48   6.253%   $220.4537   $220.45   $220.45   $220.50  
  7 purchase totals = $966.19       $1,041.3474   $1,041.35   $1,041.35   $1,041.30