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	$216.31	3.610%	$224.1188	$224.12	$224.10	$224.10
Purchase #2	$64.41	12.755%	$72.6255	$72.63	$72.65	$72.60
Purchase #3	$52.64	9.400%	$57.5882	$57.59	$57.60	$57.60
Purchase #4	$158.41	8.242%	$171.4662	$171.47	$171.45	$171.50
Purchase #5	$111.41	6.380%	$118.518	$118.52	$118.50	$118.50
Purchase #6	$122.49	6.318%	$130.2289	$130.23	$130.25	$130.20
Purchase #7	$229.73	7.658%	$247.3227	$247.32	$247.30	$247.30
7 purchase totals =	$955.40		$1,021.8683	$1,021.88	$1,021.85	$1,021.80