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	$57.59	4.360%	$60.1009	$60.10	$60.10	$60.10
Purchase #2	$144.41	10.553%	$159.6496	$159.65	$159.65	$159.60
Purchase #3	$150.32	6.836%	$160.5959	$160.60	$160.60	$160.60
Purchase #4	$47.41	13.210%	$53.6729	$53.67	$53.65	$53.70
Purchase #5	$59.26	13.420%	$67.2127	$67.21	$67.20	$67.20
Purchase #6	$202.66	3.804%	$210.3692	$210.37	$210.35	$210.40
Purchase #7	$77.92	3.810%	$80.8888	$80.89	$80.90	$80.90
7 purchase totals =	$739.57		$792.4900	$792.49	$792.45	$792.50