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	$157.33	4.631%	$164.616	$164.62	$164.60	$164.60
Purchase #2	$42.88	7.616%	$46.1457	$46.15	$46.15	$46.10
Purchase #3	$135.58	4.572%	$141.7787	$141.78	$141.80	$141.80
Purchase #4	$12.59	8.283%	$13.6328	$13.63	$13.65	$13.60
Purchase #5	$209.36	3.854%	$217.4287	$217.43	$217.45	$217.40
Purchase #6	$127.46	5.236%	$134.1338	$134.13	$134.15	$134.10
Purchase #7	$147.60	11.139%	$164.0412	$164.04	$164.05	$164.00
7 purchase totals =	$832.80		$881.7769	$881.78	$881.85	$881.60