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	$137.97	10.136%	$151.9546	$151.95	$151.95	$152.00
Purchase #2	$113.53	12.562%	$127.7916	$127.79	$127.80	$127.80
Purchase #3	$179.88	12.345%	$202.0862	$202.09	$202.10	$202.10
Purchase #4	$38.26	6.179%	$40.6241	$40.62	$40.60	$40.60
Purchase #5	$248.71	6.612%	$265.1547	$265.15	$265.15	$265.20
Purchase #6	$59.53	3.394%	$61.5504	$61.55	$61.55	$61.60
Purchase #7	$155.51	11.794%	$173.8508	$173.85	$173.85	$173.90
7 purchase totals =	$933.39		$1,023.0124	$1,023.00	$1,023.00	$1,023.20