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	$79.76	3.335%	$82.42	$82.42	$82.40	$82.40
Purchase #2	$132.41	11.166%	$147.1949	$147.19	$147.20	$147.20
Purchase #3	$200.94	3.763%	$208.5014	$208.50	$208.50	$208.50
Purchase #4	$111.31	13.310%	$126.1254	$126.13	$126.15	$126.10
Purchase #5	$159.35	4.627%	$166.7231	$166.72	$166.70	$166.70
Purchase #6	$156.37	12.288%	$175.5847	$175.58	$175.60	$175.60
Purchase #7	$166.72	9.171%	$182.0099	$182.01	$182.00	$182.00
7 purchase totals =	$1,006.86		$1,088.5594	$1,088.55	$1,088.55	$1,088.50