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	$54.46	10.791%	$60.3368	$60.34	$60.35	$60.30
Purchase #2	$100.31	6.278%	$106.6075	$106.61	$106.60	$106.60
Purchase #3	$138.34	13.760%	$157.3756	$157.38	$157.40	$157.40
Purchase #4	$82.93	7.442%	$89.1017	$89.10	$89.10	$89.10
Purchase #5	$143.91	3.199%	$148.5137	$148.51	$148.50	$148.50
Purchase #6	$142.27	13.514%	$161.4964	$161.50	$161.50	$161.50
Purchase #7	$76.95	11.460%	$85.7685	$85.77	$85.75	$85.80
7 purchase totals =	$739.17		$809.2002	$809.21	$809.20	$809.20