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	$199.40	6.644%	$212.6481	$212.65	$212.65	$212.60
Purchase #2	$50.82	7.869%	$54.819	$54.82	$54.80	$54.80
Purchase #3	$200.89	12.819%	$226.6421	$226.64	$226.65	$226.60
Purchase #4	$39.52	8.644%	$42.9361	$42.94	$42.95	$42.90
Purchase #5	$92.97	9.599%	$101.8942	$101.89	$101.90	$101.90
Purchase #6	$219.44	4.563%	$229.453	$229.45	$229.45	$229.50
Purchase #7	$93.93	7.395%	$100.8761	$100.88	$100.90	$100.90
7 purchase totals =	$896.97		$969.2686	$969.27	$969.30	$969.20