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	$136.43	11.409%	$151.9953	$152.00	$152.00	$152.00
Purchase #2	$245.58	3.147%	$253.3084	$253.31	$253.30	$253.30
Purchase #3	$181.75	5.160%	$191.1283	$191.13	$191.15	$191.10
Purchase #4	$114.55	12.490%	$128.8573	$128.86	$128.85	$128.90
Purchase #5	$166.48	13.241%	$188.5236	$188.52	$188.50	$188.50
Purchase #6	$212.46	13.629%	$241.4162	$241.42	$241.40	$241.40
Purchase #7	$125.70	5.714%	$132.8825	$132.88	$132.90	$132.90
7 purchase totals =	$1,182.95		$1,288.1116	$1,288.12	$1,288.10	$1,288.10