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	$40.53	12.827%	$45.7288	$45.73	$45.75	$45.70
Purchase #2	$82.81	10.137%	$91.2044	$91.20	$91.20	$91.20
Purchase #3	$130.64	3.256%	$134.8936	$134.89	$134.90	$134.90
Purchase #4	$139.44	6.267%	$148.1787	$148.18	$148.20	$148.20
Purchase #5	$104.62	6.663%	$111.5908	$111.59	$111.60	$111.60
Purchase #6	$242.70	13.457%	$275.3601	$275.36	$275.35	$275.40
Purchase #7	$135.73	7.448%	$145.8392	$145.84	$145.85	$145.80
7 purchase totals =	$876.47		$952.7956	$952.79	$952.85	$952.80