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	$184.72	5.795%	$195.4245	$195.42	$195.40	$195.40
Purchase #2	$81.35	5.472%	$85.8015	$85.80	$85.80	$85.80
Purchase #3	$92.33	11.737%	$103.1668	$103.17	$103.15	$103.20
Purchase #4	$168.49	12.119%	$188.9093	$188.91	$188.90	$188.90
Purchase #5	$65.91	6.826%	$70.409	$70.41	$70.40	$70.40
Purchase #6	$136.57	12.367%	$153.4596	$153.46	$153.45	$153.50
Purchase #7	$76.64	11.345%	$85.3348	$85.33	$85.35	$85.30
7 purchase totals =	$806.01		$882.5055	$882.50	$882.45	$882.50