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	$91.57	3.599%	$94.8656	$94.87	$94.85	$94.90
Purchase #2	$50.45	9.656%	$55.3215	$55.32	$55.30	$55.30
Purchase #3	$176.44	13.506%	$200.27	$200.27	$200.25	$200.30
Purchase #4	$127.52	12.775%	$143.8107	$143.81	$143.80	$143.80
Purchase #5	$12.77	11.712%	$14.2656	$14.27	$14.25	$14.30
Purchase #6	$124.33	13.842%	$141.5398	$141.54	$141.55	$141.50
Purchase #7	$224.58	7.818%	$242.1377	$242.14	$242.15	$242.10
7 purchase totals =	$807.66		$892.2109	$892.22	$892.15	$892.20