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	$244.38	7.102%	$261.7359	$261.74	$261.75	$261.70
Purchase #2	$209.62	9.525%	$229.5863	$229.59	$229.60	$229.60
Purchase #3	$99.84	13.680%	$113.4981	$113.50	$113.50	$113.50
Purchase #4	$242.47	9.461%	$265.4101	$265.41	$265.40	$265.40
Purchase #5	$95.91	9.253%	$104.7846	$104.78	$104.80	$104.80
Purchase #6	$40.45	4.695%	$42.3491	$42.35	$42.35	$42.30
Purchase #7	$22.79	6.205%	$24.2041	$24.20	$24.20	$24.20
7 purchase totals =	$955.46		$1,041.5682	$1,041.57	$1,041.60	$1,041.50