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 $59.74   5.563%   $63.0633   $63.06   $63.05   $63.10  
  Purchase #2 $152.40   8.444%   $165.2687   $165.27   $165.25   $165.30  
  Purchase #3 $34.52   13.368%   $39.1346   $39.13   $39.15   $39.10  
  Purchase #4 $204.37   13.819%   $232.6119   $232.61   $232.60   $232.60  
  Purchase #5 $124.84   10.707%   $138.2066   $138.21   $138.20   $138.20  
  Purchase #6 $218.75   10.268%   $241.2113   $241.21   $241.20   $241.20  
  Purchase #7 $225.52   10.324%   $248.8027   $248.80   $248.80   $248.80  
  7 purchase totals = $1,020.14       $1,128.2991   $1,128.29   $1,128.25   $1,128.30