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	$134.77	8.821%	$146.6581	$146.66	$146.65	$146.70
Purchase #2	$34.29	8.234%	$37.1134	$37.11	$37.10	$37.10
Purchase #3	$43.32	4.201%	$45.1399	$45.14	$45.15	$45.10
Purchase #4	$187.51	6.365%	$199.445	$199.45	$199.45	$199.40
Purchase #5	$134.31	13.603%	$152.5802	$152.58	$152.60	$152.60
Purchase #6	$89.50	7.386%	$96.1105	$96.11	$96.10	$96.10
Purchase #7	$230.69	3.462%	$238.6765	$238.68	$238.70	$238.70
7 purchase totals =	$854.39		$915.7236	$915.73	$915.75	$915.70