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	$168.40	3.154%	$173.7113	$173.71	$173.70	$173.70
Purchase #2	$30.69	3.799%	$31.8559	$31.86	$31.85	$31.90
Purchase #3	$212.54	4.160%	$221.3817	$221.38	$221.40	$221.40
Purchase #4	$139.85	11.791%	$156.3397	$156.34	$156.35	$156.30
Purchase #5	$12.41	4.502%	$12.9687	$12.97	$12.95	$13.00
Purchase #6	$10.42	13.103%	$11.7853	$11.79	$11.80	$11.80
Purchase #7	$195.86	11.538%	$218.4583	$218.46	$218.45	$218.50
7 purchase totals =	$770.17		$826.5009	$826.51	$826.50	$826.60