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	$146.87	12.522%	$165.2611	$165.26	$165.25	$165.30
Purchase #2	$172.34	9.386%	$188.5158	$188.52	$188.50	$188.50
Purchase #3	$124.41	5.515%	$131.2712	$131.27	$131.25	$131.30
Purchase #4	$82.44	5.650%	$87.0979	$87.10	$87.10	$87.10
Purchase #5	$214.90	6.829%	$229.5755	$229.58	$229.60	$229.60
Purchase #6	$244.83	12.658%	$275.8206	$275.82	$275.80	$275.80
Purchase #7	$8.33	8.468%	$9.0354	$9.04	$9.05	$9.00
7 purchase totals =	$994.12		$1,086.5775	$1,086.59	$1,086.55	$1,086.60