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	$117.87	4.511%	$123.1871	$123.19	$123.20	$123.20
Purchase #2	$99.72	11.512%	$111.1998	$111.20	$111.20	$111.20
Purchase #3	$104.51	12.147%	$117.2048	$117.20	$117.20	$117.20
Purchase #4	$47.99	13.867%	$54.6448	$54.64	$54.65	$54.60
Purchase #5	$157.88	13.160%	$178.657	$178.66	$178.65	$178.70
Purchase #6	$198.56	5.654%	$209.7866	$209.79	$209.80	$209.80
Purchase #7	$149.32	7.567%	$160.619	$160.62	$160.60	$160.60
7 purchase totals =	$875.85		$955.2991	$955.30	$955.30	$955.30