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	$221.65	8.650%	$240.8227	$240.82	$240.80	$240.80
Purchase #2	$22.41	10.817%	$24.8341	$24.83	$24.85	$24.80
Purchase #3	$205.69	8.450%	$223.0708	$223.07	$223.05	$223.10
Purchase #4	$63.65	13.711%	$72.3771	$72.38	$72.40	$72.40
Purchase #5	$158.81	4.230%	$165.5277	$165.53	$165.55	$165.50
Purchase #6	$54.66	6.626%	$58.2818	$58.28	$58.30	$58.30
Purchase #7	$215.27	13.109%	$243.4897	$243.49	$243.50	$243.50
7 purchase totals =	$942.14		$1,028.4039	$1,028.40	$1,028.45	$1,028.40