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	$176.40	4.564%	$184.4509	$184.45	$184.45	$184.50
Purchase #2	$36.32	3.248%	$37.4997	$37.50	$37.50	$37.50
Purchase #3	$47.91	11.575%	$53.4556	$53.46	$53.45	$53.50
Purchase #4	$132.32	10.256%	$145.8907	$145.89	$145.90	$145.90
Purchase #5	$138.73	8.359%	$150.3264	$150.33	$150.35	$150.30
Purchase #6	$69.50	5.302%	$73.1849	$73.18	$73.20	$73.20
Purchase #7	$19.28	10.666%	$21.3364	$21.34	$21.35	$21.30
7 purchase totals =	$620.46		$666.1446	$666.15	$666.20	$666.20