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	$225.45	4.653%	$235.9402	$235.94	$235.95	$235.90
Purchase #2	$92.78	11.175%	$103.1482	$103.15	$103.15	$103.10
Purchase #3	$88.60	7.584%	$95.3194	$95.32	$95.30	$95.30
Purchase #4	$111.96	8.400%	$121.3646	$121.36	$121.35	$121.40
Purchase #5	$159.42	13.502%	$180.9449	$180.94	$180.95	$180.90
Purchase #6	$184.65	11.257%	$205.4361	$205.44	$205.45	$205.40
Purchase #7	$56.33	5.711%	$59.547	$59.55	$59.55	$59.50
7 purchase totals =	$919.19		$1,001.7004	$1,001.70	$1,001.70	$1,001.50