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	$80.92	7.690%	$87.1427	$87.14	$87.15	$87.10
Purchase #2	$41.91	9.629%	$45.9455	$45.95	$45.95	$45.90
Purchase #3	$225.37	5.760%	$238.3513	$238.35	$238.35	$238.40
Purchase #4	$241.49	13.599%	$274.3302	$274.33	$274.35	$274.30
Purchase #5	$61.67	8.417%	$66.8608	$66.86	$66.85	$66.90
Purchase #6	$144.74	10.863%	$160.4631	$160.46	$160.45	$160.50
Purchase #7	$172.25	6.402%	$183.2774	$183.28	$183.30	$183.30
7 purchase totals =	$968.35		$1,056.3710	$1,056.37	$1,056.40	$1,056.40