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	$228.29	4.105%	$237.6613	$237.66	$237.65	$237.70
Purchase #2	$80.56	6.715%	$85.9696	$85.97	$85.95	$86.00
Purchase #3	$208.91	7.116%	$223.776	$223.78	$223.80	$223.80
Purchase #4	$193.83	6.180%	$205.8087	$205.81	$205.80	$205.80
Purchase #5	$199.78	9.558%	$218.875	$218.88	$218.90	$218.90
Purchase #6	$167.66	13.613%	$190.4836	$190.48	$190.50	$190.50
Purchase #7	$126.79	8.349%	$137.3757	$137.38	$137.40	$137.40
7 purchase totals =	$1,205.82		$1,299.9499	$1,299.96	$1,300.00	$1,300.10