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	$149.91	11.540%	$167.2096	$167.21	$167.20	$167.20
Purchase #2	$6.46	10.547%	$7.1413	$7.14	$7.15	$7.10
Purchase #3	$164.51	4.765%	$172.3489	$172.35	$172.35	$172.30
Purchase #4	$181.89	13.340%	$206.1541	$206.15	$206.15	$206.20
Purchase #5	$137.66	7.406%	$147.8551	$147.86	$147.85	$147.90
Purchase #6	$135.42	5.595%	$142.9967	$143.00	$143.00	$143.00
Purchase #7	$149.50	6.760%	$159.6062	$159.61	$159.60	$159.60
7 purchase totals =	$925.35		$1,003.3119	$1,003.32	$1,003.30	$1,003.30