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	$142.47	7.138%	$152.6395	$152.64	$152.65	$152.60
Purchase #2	$223.29	13.532%	$253.5056	$253.51	$253.50	$253.50
Purchase #3	$126.35	7.872%	$136.2963	$136.30	$136.30	$136.30
Purchase #4	$169.88	7.540%	$182.689	$182.69	$182.70	$182.70
Purchase #5	$136.71	10.346%	$150.854	$150.85	$150.85	$150.90
Purchase #6	$20.73	5.171%	$21.8019	$21.80	$21.80	$21.80
Purchase #7	$142.45	9.685%	$156.2463	$156.25	$156.25	$156.20
7 purchase totals =	$961.88		$1,054.0326	$1,054.04	$1,054.05	$1,054.00