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	$201.32	10.712%	$222.8854	$222.89	$222.90	$222.90
Purchase #2	$175.85	7.783%	$189.5364	$189.54	$189.55	$189.50
Purchase #3	$232.31	5.261%	$244.5318	$244.53	$244.55	$244.50
Purchase #4	$188.77	5.530%	$199.209	$199.21	$199.20	$199.20
Purchase #5	$158.80	11.288%	$176.7253	$176.73	$176.75	$176.70
Purchase #6	$18.38	11.333%	$20.463	$20.46	$20.45	$20.50
Purchase #7	$250.90	10.262%	$276.6474	$276.65	$276.65	$276.60
7 purchase totals =	$1,226.33		$1,329.9983	$1,330.01	$1,330.05	$1,329.90