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	$141.94	9.231%	$155.0425	$155.04	$155.05	$155.00
Purchase #2	$44.83	13.620%	$50.9358	$50.94	$50.95	$50.90
Purchase #3	$28.44	4.696%	$29.7755	$29.78	$29.80	$29.80
Purchase #4	$218.85	5.185%	$230.1974	$230.20	$230.20	$230.20
Purchase #5	$219.90	9.824%	$241.503	$241.50	$241.50	$241.50
Purchase #6	$248.71	7.713%	$267.893	$267.89	$267.90	$267.90
Purchase #7	$39.27	8.487%	$42.6028	$42.60	$42.60	$42.60
7 purchase totals =	$941.94		$1,017.9500	$1,017.95	$1,018.00	$1,017.90