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	$115.48	11.205%	$128.4195	$128.42	$128.40	$128.40
Purchase #2	$170.30	4.860%	$178.5766	$178.58	$178.60	$178.60
Purchase #3	$193.76	10.103%	$213.3356	$213.34	$213.35	$213.30
Purchase #4	$217.39	13.313%	$246.3311	$246.33	$246.35	$246.30
Purchase #5	$9.51	9.123%	$10.3776	$10.38	$10.40	$10.40
Purchase #6	$79.91	13.377%	$90.5996	$90.60	$90.60	$90.60
Purchase #7	$145.74	4.694%	$152.581	$152.58	$152.60	$152.60
7 purchase totals =	$932.09		$1,020.2210	$1,020.23	$1,020.30	$1,020.20