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	$136.85	11.345%	$152.3756	$152.38	$152.40	$152.40
Purchase #2	$65.72	3.479%	$68.0064	$68.01	$68.00	$68.00
Purchase #3	$137.79	5.581%	$145.4801	$145.48	$145.50	$145.50
Purchase #4	$111.86	10.758%	$123.8939	$123.89	$123.90	$123.90
Purchase #5	$60.90	5.205%	$64.0698	$64.07	$64.05	$64.10
Purchase #6	$62.38	7.387%	$66.988	$66.99	$67.00	$67.00
Purchase #7	$94.44	6.846%	$100.9054	$100.91	$100.90	$100.90
7 purchase totals =	$669.94		$721.7192	$721.73	$721.75	$721.80