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	$61.64	7.473%	$66.2464	$66.25	$66.25	$66.20
Purchase #2	$243.30	8.716%	$264.506	$264.51	$264.50	$264.50
Purchase #3	$76.66	13.863%	$87.2874	$87.29	$87.30	$87.30
Purchase #4	$207.90	8.519%	$225.611	$225.61	$225.60	$225.60
Purchase #5	$101.43	10.604%	$112.1856	$112.19	$112.20	$112.20
Purchase #6	$181.68	3.722%	$188.4421	$188.44	$188.45	$188.40
Purchase #7	$211.25	5.235%	$222.3089	$222.31	$222.30	$222.30
7 purchase totals =	$1,083.86		$1,166.5874	$1,166.60	$1,166.60	$1,166.50