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	$162.73	6.227%	$172.8632	$172.86	$172.85	$172.90
Purchase #2	$17.85	5.527%	$18.8366	$18.84	$18.85	$18.80
Purchase #3	$165.68	12.144%	$185.8002	$185.80	$185.80	$185.80
Purchase #4	$44.50	13.447%	$50.4839	$50.48	$50.50	$50.50
Purchase #5	$33.38	4.428%	$34.8581	$34.86	$34.85	$34.90
Purchase #6	$28.61	13.138%	$32.3688	$32.37	$32.35	$32.40
Purchase #7	$206.96	9.387%	$226.3873	$226.39	$226.40	$226.40
7 purchase totals =	$659.71		$721.5981	$721.60	$721.60	$721.70