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	$146.78	8.726%	$159.588	$159.59	$159.60	$159.60
Purchase #2	$64.32	4.683%	$67.3321	$67.33	$67.35	$67.30
Purchase #3	$159.60	3.764%	$165.6073	$165.61	$165.60	$165.60
Purchase #4	$177.79	7.341%	$190.8416	$190.84	$190.85	$190.80
Purchase #5	$169.35	9.780%	$185.9124	$185.91	$185.90	$185.90
Purchase #6	$116.27	12.466%	$130.7642	$130.76	$130.75	$130.80
Purchase #7	$126.75	11.209%	$140.9574	$140.96	$140.95	$141.00
7 purchase totals =	$960.86		$1,041.0030	$1,041.00	$1,041.00	$1,041.00