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	$237.86	12.120%	$266.6886	$266.69	$266.70	$266.70
Purchase #2	$223.37	11.249%	$248.4969	$248.50	$248.50	$248.50
Purchase #3	$78.69	4.702%	$82.39	$82.39	$82.40	$82.40
Purchase #4	$124.35	13.606%	$141.2691	$141.27	$141.25	$141.30
Purchase #5	$145.95	8.650%	$158.5747	$158.57	$158.55	$158.60
Purchase #6	$83.74	8.160%	$90.5732	$90.57	$90.55	$90.60
Purchase #7	$18.52	11.613%	$20.6707	$20.67	$20.65	$20.70
7 purchase totals =	$912.48		$1,008.6632	$1,008.66	$1,008.60	$1,008.80