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	$230.58	3.395%	$238.4082	$238.41	$238.40	$238.40
Purchase #2	$91.28	11.576%	$101.8466	$101.85	$101.85	$101.80
Purchase #3	$105.87	13.443%	$120.1021	$120.10	$120.10	$120.10
Purchase #4	$178.70	13.234%	$202.3492	$202.35	$202.35	$202.30
Purchase #5	$142.62	10.689%	$157.8647	$157.86	$157.85	$157.90
Purchase #6	$124.56	6.388%	$132.5169	$132.52	$132.50	$132.50
Purchase #7	$99.84	11.373%	$111.1948	$111.19	$111.20	$111.20
7 purchase totals =	$973.45		$1,064.2825	$1,064.28	$1,064.25	$1,064.20