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	$80.94	5.673%	$85.5317	$85.53	$85.55	$85.50
Purchase #2	$164.81	7.528%	$177.2169	$177.22	$177.20	$177.20
Purchase #3	$53.89	13.808%	$61.3311	$61.33	$61.35	$61.30
Purchase #4	$22.64	11.848%	$25.3224	$25.32	$25.30	$25.30
Purchase #5	$111.66	7.532%	$120.0702	$120.07	$120.05	$120.10
Purchase #6	$242.85	4.704%	$254.2737	$254.27	$254.25	$254.30
Purchase #7	$124.66	12.231%	$139.9072	$139.91	$139.90	$139.90
7 purchase totals =	$801.45		$863.6532	$863.65	$863.60	$863.60