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	$215.78	6.198%	$229.154	$229.15	$229.15	$229.20
Purchase #2	$34.47	9.224%	$37.6495	$37.65	$37.65	$37.60
Purchase #3	$49.80	8.861%	$54.2128	$54.21	$54.20	$54.20
Purchase #4	$93.80	6.808%	$100.1859	$100.19	$100.20	$100.20
Purchase #5	$25.35	11.137%	$28.1732	$28.17	$28.15	$28.20
Purchase #6	$126.27	12.685%	$142.2873	$142.29	$142.30	$142.30
Purchase #7	$27.64	13.313%	$31.3197	$31.32	$31.30	$31.30
7 purchase totals =	$573.11		$622.9824	$622.98	$622.95	$623.00