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	$132.60	10.345%	$146.3175	$146.32	$146.30	$146.30
Purchase #2	$38.84	3.728%	$40.288	$40.29	$40.30	$40.30
Purchase #3	$241.52	9.333%	$264.0611	$264.06	$264.05	$264.10
Purchase #4	$107.85	9.518%	$118.1152	$118.12	$118.10	$118.10
Purchase #5	$129.34	5.691%	$136.7007	$136.70	$136.70	$136.70
Purchase #6	$208.89	10.356%	$230.5226	$230.52	$230.50	$230.50
Purchase #7	$136.79	10.250%	$150.811	$150.81	$150.80	$150.80
7 purchase totals =	$995.83		$1,086.8161	$1,086.82	$1,086.75	$1,086.80