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	$171.63	8.472%	$186.1705	$186.17	$186.15	$186.20
Purchase #2	$166.26	3.620%	$172.2786	$172.28	$172.30	$172.30
Purchase #3	$59.58	4.612%	$62.3278	$62.33	$62.35	$62.30
Purchase #4	$189.77	12.523%	$213.5349	$213.53	$213.55	$213.50
Purchase #5	$227.69	3.455%	$235.5567	$235.56	$235.55	$235.60
Purchase #6	$167.56	12.476%	$188.4648	$188.46	$188.45	$188.50
Purchase #7	$223.64	13.534%	$253.9074	$253.91	$253.90	$253.90
7 purchase totals =	$1,206.13		$1,312.2407	$1,312.24	$1,312.25	$1,312.30