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	$134.93	4.674%	$141.2366	$141.24	$141.25	$141.20
Purchase #2	$127.56	5.775%	$134.9266	$134.93	$134.95	$134.90
Purchase #3	$146.31	13.768%	$166.454	$166.45	$166.45	$166.50
Purchase #4	$239.28	6.809%	$255.5726	$255.57	$255.55	$255.60
Purchase #5	$205.76	5.368%	$216.8052	$216.81	$216.80	$216.80
Purchase #6	$125.29	12.639%	$141.1254	$141.13	$141.15	$141.10
Purchase #7	$9.99	3.483%	$10.338	$10.34	$10.35	$10.30
7 purchase totals =	$989.12		$1,066.4584	$1,066.47	$1,066.50	$1,066.40