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	$144.64	3.861%	$150.2246	$150.22	$150.20	$150.20
Purchase #2	$37.45	10.205%	$41.2718	$41.27	$41.25	$41.30
Purchase #3	$40.33	13.244%	$45.6713	$45.67	$45.65	$45.70
Purchase #4	$227.49	12.453%	$255.8193	$255.82	$255.80	$255.80
Purchase #5	$184.53	3.863%	$191.6584	$191.66	$191.65	$191.70
Purchase #6	$191.72	4.399%	$200.1538	$200.15	$200.15	$200.20
Purchase #7	$222.30	10.688%	$246.0594	$246.06	$246.05	$246.10
7 purchase totals =	$1,048.46		$1,130.8586	$1,130.85	$1,130.75	$1,131.00