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	$131.63	7.222%	$141.1363	$141.14	$141.15	$141.10
Purchase #2	$149.67	6.857%	$159.9329	$159.93	$159.95	$159.90
Purchase #3	$61.68	6.113%	$65.4505	$65.45	$65.45	$65.50
Purchase #4	$187.96	4.288%	$196.0197	$196.02	$196.00	$196.00
Purchase #5	$228.55	4.844%	$239.621	$239.62	$239.60	$239.60
Purchase #6	$145.48	4.863%	$152.5547	$152.55	$152.55	$152.60
Purchase #7	$152.32	8.160%	$164.7493	$164.75	$164.75	$164.70
7 purchase totals =	$1,057.29		$1,119.4644	$1,119.46	$1,119.45	$1,119.40