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	$101.85	12.394%	$114.4733	$114.47	$114.45	$114.50
Purchase #2	$130.41	13.650%	$148.211	$148.21	$148.20	$148.20
Purchase #3	$166.50	11.304%	$185.3212	$185.32	$185.30	$185.30
Purchase #4	$151.46	8.304%	$164.0372	$164.04	$164.05	$164.00
Purchase #5	$158.39	6.384%	$168.5016	$168.50	$168.50	$168.50
Purchase #6	$207.75	5.581%	$219.3445	$219.34	$219.35	$219.30
Purchase #7	$206.78	6.125%	$219.4453	$219.45	$219.45	$219.40
7 purchase totals =	$1,123.14		$1,219.3341	$1,219.33	$1,219.30	$1,219.20