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	$48.75	7.504%	$52.4082	$52.41	$52.40	$52.40
Purchase #2	$165.70	11.689%	$185.0687	$185.07	$185.05	$185.10
Purchase #3	$90.98	5.343%	$95.8411	$95.84	$95.85	$95.80
Purchase #4	$60.77	5.274%	$63.975	$63.98	$64.00	$64.00
Purchase #5	$37.29	13.303%	$42.2507	$42.25	$42.25	$42.30
Purchase #6	$9.44	6.185%	$10.0239	$10.02	$10.00	$10.00
Purchase #7	$67.96	7.564%	$73.1005	$73.10	$73.10	$73.10
7 purchase totals =	$480.89		$522.6681	$522.67	$522.65	$522.70