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	$181.80	12.359%	$204.2687	$204.27	$204.25	$204.30
Purchase #2	$109.73	8.212%	$118.741	$118.74	$118.75	$118.70
Purchase #3	$220.65	8.837%	$240.1488	$240.15	$240.15	$240.10
Purchase #4	$146.27	4.544%	$152.9165	$152.92	$152.90	$152.90
Purchase #5	$59.34	12.583%	$66.8068	$66.81	$66.80	$66.80
Purchase #6	$61.38	9.680%	$67.3216	$67.32	$67.30	$67.30
Purchase #7	$223.79	13.286%	$253.5227	$253.52	$253.50	$253.50
7 purchase totals =	$1,002.96		$1,103.7261	$1,103.73	$1,103.65	$1,103.60