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	$161.95	11.625%	$180.7767	$180.78	$180.80	$180.80
Purchase #2	$139.42	5.706%	$147.3753	$147.38	$147.40	$147.40
Purchase #3	$47.67	13.849%	$54.2718	$54.27	$54.25	$54.30
Purchase #4	$35.27	10.309%	$38.906	$38.91	$38.90	$38.90
Purchase #5	$178.39	13.324%	$202.1587	$202.16	$202.15	$202.20
Purchase #6	$167.72	10.369%	$185.1109	$185.11	$185.10	$185.10
Purchase #7	$214.52	4.145%	$223.4119	$223.41	$223.40	$223.40
7 purchase totals =	$944.94		$1,032.0113	$1,032.02	$1,032.00	$1,032.10