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	$147.51	4.295%	$153.8456	$153.85	$153.85	$153.80
Purchase #2	$85.44	4.520%	$89.3019	$89.30	$89.30	$89.30
Purchase #3	$122.31	11.820%	$136.767	$136.77	$136.75	$136.80
Purchase #4	$138.25	9.388%	$151.2289	$151.23	$151.25	$151.20
Purchase #5	$161.66	3.198%	$166.8299	$166.83	$166.85	$166.80
Purchase #6	$221.86	3.216%	$228.995	$229.00	$229.00	$229.00
Purchase #7	$25.68	11.497%	$28.6324	$28.63	$28.65	$28.60
7 purchase totals =	$902.71		$955.6007	$955.61	$955.65	$955.50