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	$93.28	7.859%	$100.6109	$100.61	$100.60	$100.60
Purchase #2	$127.59	11.255%	$141.9503	$141.95	$141.95	$142.00
Purchase #3	$33.85	3.462%	$35.0219	$35.02	$35.00	$35.00
Purchase #4	$172.63	7.503%	$185.5824	$185.58	$185.60	$185.60
Purchase #5	$126.35	8.530%	$137.1277	$137.13	$137.15	$137.10
Purchase #6	$109.46	4.513%	$114.3999	$114.40	$114.40	$114.40
Purchase #7	$164.26	3.671%	$170.29	$170.29	$170.30	$170.30
7 purchase totals =	$827.42		$884.9831	$884.98	$885.00	$885.00