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	$141.31	4.489%	$147.6534	$147.65	$147.65	$147.70
Purchase #2	$243.42	5.386%	$256.5306	$256.53	$256.55	$256.50
Purchase #3	$152.29	12.104%	$170.7232	$170.72	$170.70	$170.70
Purchase #4	$99.85	4.102%	$103.9458	$103.95	$103.95	$103.90
Purchase #5	$153.67	3.345%	$158.8103	$158.81	$158.80	$158.80
Purchase #6	$88.30	12.639%	$99.4602	$99.46	$99.45	$99.50
Purchase #7	$153.95	9.154%	$168.0426	$168.04	$168.05	$168.00
7 purchase totals =	$1,032.79		$1,105.1661	$1,105.16	$1,105.15	$1,105.10