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	$247.57	6.839%	$264.5013	$264.50	$264.50	$264.50
Purchase #2	$63.37	12.754%	$71.4522	$71.45	$71.45	$71.50
Purchase #3	$18.41	3.261%	$19.0104	$19.01	$19.00	$19.00
Purchase #4	$100.41	3.423%	$103.847	$103.85	$103.85	$103.80
Purchase #5	$223.48	13.278%	$253.1537	$253.15	$253.15	$253.20
Purchase #6	$199.29	12.183%	$223.5695	$223.57	$223.55	$223.60
Purchase #7	$109.68	6.574%	$116.8904	$116.89	$116.90	$116.90
7 purchase totals =	$962.21		$1,052.4245	$1,052.42	$1,052.40	$1,052.50