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	$223.81	8.487%	$242.8048	$242.80	$242.80	$242.80
Purchase #2	$74.91	13.787%	$85.2378	$85.24	$85.25	$85.20
Purchase #3	$78.93	11.659%	$88.1324	$88.13	$88.15	$88.10
Purchase #4	$245.38	4.244%	$255.7939	$255.79	$255.80	$255.80
Purchase #5	$105.59	4.750%	$110.6055	$110.61	$110.60	$110.60
Purchase #6	$176.53	13.506%	$200.3721	$200.37	$200.35	$200.40
Purchase #7	$246.73	7.517%	$265.2767	$265.28	$265.30	$265.30
7 purchase totals =	$1,151.88		$1,248.2232	$1,248.22	$1,248.25	$1,248.20