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	$149.25	4.534%	$156.017	$156.02	$156.00	$156.00
Purchase #2	$149.92	10.199%	$165.2103	$165.21	$165.20	$165.20
Purchase #3	$182.79	6.628%	$194.9053	$194.91	$194.90	$194.90
Purchase #4	$133.45	13.612%	$151.6152	$151.62	$151.60	$151.60
Purchase #5	$155.75	11.243%	$173.261	$173.26	$173.25	$173.30
Purchase #6	$80.26	11.570%	$89.5461	$89.55	$89.55	$89.50
Purchase #7	$37.60	13.660%	$42.7362	$42.74	$42.75	$42.70
7 purchase totals =	$889.02		$973.2911	$973.31	$973.25	$973.20