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	$45.25	4.211%	$47.1555	$47.16	$47.15	$47.20
Purchase #2	$89.53	6.536%	$95.3817	$95.38	$95.40	$95.40
Purchase #3	$223.78	6.512%	$238.3526	$238.35	$238.35	$238.40
Purchase #4	$32.74	13.428%	$37.1363	$37.14	$37.15	$37.10
Purchase #5	$88.44	12.217%	$99.2447	$99.24	$99.25	$99.20
Purchase #6	$32.75	8.122%	$35.41	$35.41	$35.40	$35.40
Purchase #7	$171.71	10.240%	$189.2931	$189.29	$189.30	$189.30
7 purchase totals =	$684.20		$741.9739	$741.97	$742.00	$742.00