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	$147.44	6.651%	$157.2462	$157.25	$157.25	$157.20
Purchase #2	$127.73	11.784%	$142.7817	$142.78	$142.80	$142.80
Purchase #3	$89.66	11.113%	$99.6239	$99.62	$99.60	$99.60
Purchase #4	$39.39	7.149%	$42.206	$42.21	$42.20	$42.20
Purchase #5	$88.38	5.390%	$93.1437	$93.14	$93.15	$93.10
Purchase #6	$71.28	3.546%	$73.8076	$73.81	$73.80	$73.80
Purchase #7	$140.30	9.377%	$153.4559	$153.46	$153.45	$153.50
7 purchase totals =	$704.18		$762.2650	$762.27	$762.25	$762.20