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	$61.63	4.657%	$64.5001	$64.50	$64.50	$64.50
Purchase #2	$157.28	3.519%	$162.8147	$162.81	$162.80	$162.80
Purchase #3	$157.65	7.417%	$169.3429	$169.34	$169.35	$169.30
Purchase #4	$153.95	9.397%	$168.4167	$168.42	$168.40	$168.40
Purchase #5	$148.67	11.517%	$165.7923	$165.79	$165.80	$165.80
Purchase #6	$25.85	11.321%	$28.7765	$28.78	$28.80	$28.80
Purchase #7	$233.82	3.763%	$242.6186	$242.62	$242.60	$242.60
7 purchase totals =	$938.85		$1,002.2618	$1,002.26	$1,002.25	$1,002.20