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 $48.62   8.585%   $52.794   $52.79   $52.80   $52.80  
  Purchase #2 $215.49   9.199%   $235.3129   $235.31   $235.30   $235.30  
  Purchase #3 $155.51   7.131%   $166.5994   $166.60   $166.60   $166.60  
  Purchase #4 $113.58   6.319%   $120.7571   $120.76   $120.75   $120.80  
  Purchase #5 $212.55   10.292%   $234.4256   $234.43   $234.45   $234.40  
  Purchase #6 $94.49   8.337%   $102.3676   $102.37   $102.35   $102.40  
  Purchase #7 $234.90   3.727%   $243.6547   $243.65   $243.65   $243.70  
  7 purchase totals = $1,075.14       $1,155.9113   $1,155.91   $1,155.90   $1,156.00