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	$119.25	3.530%	$123.4595	$123.46	$123.45	$123.50
Purchase #2	$33.88	4.245%	$35.3182	$35.32	$35.30	$35.30
Purchase #3	$10.31	4.459%	$10.7697	$10.77	$10.75	$10.80
Purchase #4	$171.45	10.777%	$189.9272	$189.93	$189.95	$189.90
Purchase #5	$22.29	11.558%	$24.8663	$24.87	$24.85	$24.90
Purchase #6	$58.72	5.143%	$61.74	$61.74	$61.75	$61.70
Purchase #7	$248.92	8.589%	$270.2997	$270.30	$270.30	$270.30
7 purchase totals =	$664.82		$716.3806	$716.39	$716.35	$716.40