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	$132.48	8.734%	$144.0508	$144.05	$144.05	$144.10
Purchase #2	$142.73	10.332%	$157.4769	$157.48	$157.50	$157.50
Purchase #3	$233.81	4.421%	$244.1467	$244.15	$244.15	$244.10
Purchase #4	$71.53	9.268%	$78.1594	$78.16	$78.15	$78.20
Purchase #5	$28.59	11.705%	$31.9365	$31.94	$31.95	$31.90
Purchase #6	$38.30	10.743%	$42.4146	$42.41	$42.40	$42.40
Purchase #7	$95.38	9.181%	$104.1368	$104.14	$104.15	$104.10
7 purchase totals =	$742.82		$802.3217	$802.33	$802.35	$802.30