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	$97.30	12.191%	$109.1618	$109.16	$109.15	$109.20
Purchase #2	$85.30	10.561%	$94.3085	$94.31	$94.30	$94.30
Purchase #3	$32.45	6.468%	$34.5489	$34.55	$34.55	$34.50
Purchase #4	$33.38	12.777%	$37.645	$37.65	$37.65	$37.60
Purchase #5	$234.29	5.229%	$246.541	$246.54	$246.55	$246.50
Purchase #6	$98.27	13.555%	$111.5905	$111.59	$111.60	$111.60
Purchase #7	$105.82	12.421%	$118.9639	$118.96	$118.95	$119.00
7 purchase totals =	$686.81		$752.7596	$752.76	$752.75	$752.70