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	$164.59	12.486%	$185.1407	$185.14	$185.15	$185.10
Purchase #2	$170.80	12.157%	$191.5642	$191.56	$191.55	$191.60
Purchase #3	$59.58	11.659%	$66.5264	$66.53	$66.55	$66.50
Purchase #4	$151.44	11.773%	$169.269	$169.27	$169.25	$169.30
Purchase #5	$134.54	7.605%	$144.7718	$144.77	$144.75	$144.80
Purchase #6	$52.98	4.654%	$55.4457	$55.45	$55.45	$55.40
Purchase #7	$149.87	5.788%	$158.5445	$158.54	$158.55	$158.50
7 purchase totals =	$883.80		$971.2623	$971.26	$971.25	$971.20