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	$86.51	4.446%	$90.3562	$90.36	$90.35	$90.40
Purchase #2	$213.90	4.410%	$223.333	$223.33	$223.35	$223.30
Purchase #3	$20.77	8.595%	$22.5552	$22.56	$22.55	$22.60
Purchase #4	$138.76	11.423%	$154.6106	$154.61	$154.60	$154.60
Purchase #5	$160.67	7.322%	$172.4343	$172.43	$172.45	$172.40
Purchase #6	$199.74	3.384%	$206.4992	$206.50	$206.50	$206.50
Purchase #7	$77.93	10.674%	$86.2482	$86.25	$86.25	$86.20
7 purchase totals =	$898.28		$956.0367	$956.04	$956.05	$956.00