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	$147.57	3.195%	$152.2849	$152.28	$152.30	$152.30
Purchase #2	$37.58	9.428%	$41.123	$41.12	$41.10	$41.10
Purchase #3	$43.66	11.286%	$48.5875	$48.59	$48.60	$48.60
Purchase #4	$88.68	13.410%	$100.572	$100.57	$100.55	$100.60
Purchase #5	$94.89	4.402%	$99.0671	$99.07	$99.05	$99.10
Purchase #6	$219.47	11.135%	$243.908	$243.91	$243.90	$243.90
Purchase #7	$175.28	12.757%	$197.6405	$197.64	$197.65	$197.60
7 purchase totals =	$807.13		$883.1830	$883.18	$883.15	$883.20