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	$105.57	12.520%	$118.7874	$118.79	$118.80	$118.80
Purchase #2	$80.70	6.390%	$85.8567	$85.86	$85.85	$85.90
Purchase #3	$220.52	9.406%	$241.2621	$241.26	$241.25	$241.30
Purchase #4	$141.71	7.610%	$152.4941	$152.49	$152.50	$152.50
Purchase #5	$175.72	5.278%	$184.9945	$184.99	$185.00	$185.00
Purchase #6	$50.86	10.229%	$56.0625	$56.06	$56.05	$56.10
Purchase #7	$152.65	12.863%	$172.2854	$172.29	$172.30	$172.30
7 purchase totals =	$927.73		$1,011.7427	$1,011.74	$1,011.75	$1,011.90