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	$144.72	3.542%	$149.846	$149.85	$149.85	$149.80
Purchase #2	$161.39	3.754%	$167.4486	$167.45	$167.45	$167.40
Purchase #3	$29.74	4.359%	$31.0364	$31.04	$31.05	$31.00
Purchase #4	$157.51	11.369%	$175.4173	$175.42	$175.40	$175.40
Purchase #5	$109.78	5.198%	$115.4864	$115.49	$115.50	$115.50
Purchase #6	$166.95	10.798%	$184.9773	$184.98	$185.00	$185.00
Purchase #7	$170.86	12.332%	$191.9305	$191.93	$191.95	$191.90
7 purchase totals =	$940.95		$1,016.1425	$1,016.16	$1,016.20	$1,016.00