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	$248.29	10.669%	$274.7801	$274.78	$274.80	$274.80
Purchase #2	$34.32	5.131%	$36.081	$36.08	$36.10	$36.10
Purchase #3	$148.76	9.210%	$162.4608	$162.46	$162.45	$162.50
Purchase #4	$31.80	11.149%	$35.3454	$35.35	$35.35	$35.30
Purchase #5	$95.50	4.240%	$99.5492	$99.55	$99.55	$99.50
Purchase #6	$11.53	3.744%	$11.9617	$11.96	$11.95	$12.00
Purchase #7	$101.33	10.447%	$111.9159	$111.92	$111.90	$111.90
7 purchase totals =	$671.53		$732.0941	$732.10	$732.10	$732.10