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	$179.43	9.455%	$196.3951	$196.40	$196.40	$196.40
Purchase #2	$144.75	4.388%	$151.1016	$151.10	$151.10	$151.10
Purchase #3	$248.37	7.140%	$266.1036	$266.10	$266.10	$266.10
Purchase #4	$7.91	9.354%	$8.6499	$8.65	$8.65	$8.60
Purchase #5	$149.82	10.281%	$165.223	$165.22	$165.20	$165.20
Purchase #6	$209.27	12.434%	$235.2906	$235.29	$235.30	$235.30
Purchase #7	$19.79	5.670%	$20.9121	$20.91	$20.90	$20.90
7 purchase totals =	$959.34		$1,043.6759	$1,043.67	$1,043.65	$1,043.60