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	$61.40	8.378%	$66.5441	$66.54	$66.55	$66.50
Purchase #2	$56.86	8.217%	$61.5322	$61.53	$61.55	$61.50
Purchase #3	$149.61	10.711%	$165.6347	$165.63	$165.65	$165.60
Purchase #4	$99.55	11.519%	$111.0172	$111.02	$111.00	$111.00
Purchase #5	$14.46	3.683%	$14.9926	$14.99	$15.00	$15.00
Purchase #6	$178.60	13.851%	$203.3379	$203.34	$203.35	$203.30
Purchase #7	$204.92	4.218%	$213.5635	$213.56	$213.55	$213.60
7 purchase totals =	$765.40		$836.6222	$836.61	$836.65	$836.50