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	$189.78	8.182%	$205.3078	$205.31	$205.30	$205.30
Purchase #2	$139.75	3.369%	$144.4582	$144.46	$144.45	$144.50
Purchase #3	$85.52	11.120%	$95.0298	$95.03	$95.05	$95.00
Purchase #4	$106.45	11.733%	$118.9398	$118.94	$118.95	$118.90
Purchase #5	$216.55	4.199%	$225.6429	$225.64	$225.65	$225.60
Purchase #6	$213.74	4.576%	$223.5207	$223.52	$223.50	$223.50
Purchase #7	$100.65	4.811%	$105.4923	$105.49	$105.50	$105.50
7 purchase totals =	$1,052.44		$1,118.3915	$1,118.39	$1,118.40	$1,118.30