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	$215.86	3.186%	$222.7373	$222.74	$222.75	$222.70
Purchase #2	$90.95	3.539%	$94.1687	$94.17	$94.15	$94.20
Purchase #3	$242.64	3.641%	$251.4745	$251.47	$251.45	$251.50
Purchase #4	$18.33	12.639%	$20.6467	$20.65	$20.65	$20.60
Purchase #5	$146.99	12.369%	$165.1712	$165.17	$165.15	$165.20
Purchase #6	$91.60	13.554%	$104.0155	$104.02	$104.00	$104.00
Purchase #7	$113.30	6.348%	$120.4923	$120.49	$120.50	$120.50
7 purchase totals =	$919.67		$978.7062	$978.71	$978.65	$978.70