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	$138.82	7.294%	$148.9455	$148.95	$148.95	$148.90
Purchase #2	$233.34	7.479%	$250.7915	$250.79	$250.80	$250.80
Purchase #3	$117.73	7.710%	$126.807	$126.81	$126.80	$126.80
Purchase #4	$128.92	8.228%	$139.5275	$139.53	$139.55	$139.50
Purchase #5	$54.74	8.602%	$59.4487	$59.45	$59.45	$59.40
Purchase #6	$196.69	4.458%	$205.4584	$205.46	$205.45	$205.50
Purchase #7	$20.77	11.541%	$23.1671	$23.17	$23.15	$23.20
7 purchase totals =	$891.01		$954.1457	$954.16	$954.15	$954.10