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	$159.34	4.458%	$166.4434	$166.44	$166.45	$166.40
Purchase #2	$156.76	5.722%	$165.7298	$165.73	$165.75	$165.70
Purchase #3	$144.85	13.764%	$164.7872	$164.79	$164.80	$164.80
Purchase #4	$32.50	5.679%	$34.3457	$34.35	$34.35	$34.30
Purchase #5	$85.56	11.494%	$95.3943	$95.39	$95.40	$95.40
Purchase #6	$32.87	6.772%	$35.096	$35.10	$35.10	$35.10
Purchase #7	$39.90	13.773%	$45.3954	$45.40	$45.40	$45.40
7 purchase totals =	$651.78		$707.1918	$707.20	$707.25	$707.10