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	$89.65	4.150%	$93.3705	$93.37	$93.35	$93.40
Purchase #2	$223.87	13.426%	$253.9268	$253.93	$253.95	$253.90
Purchase #3	$117.78	8.574%	$127.8785	$127.88	$127.90	$127.90
Purchase #4	$109.77	11.542%	$122.4397	$122.44	$122.45	$122.40
Purchase #5	$195.47	13.360%	$221.5848	$221.58	$221.60	$221.60
Purchase #6	$231.74	9.399%	$253.5212	$253.52	$253.50	$253.50
Purchase #7	$33.98	11.661%	$37.9424	$37.94	$37.95	$37.90
7 purchase totals =	$1,002.26		$1,110.6639	$1,110.66	$1,110.70	$1,110.60