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	$117.75	5.737%	$124.5053	$124.51	$124.50	$124.50
Purchase #2	$90.84	9.227%	$99.2218	$99.22	$99.20	$99.20
Purchase #3	$18.60	11.675%	$20.7716	$20.77	$20.75	$20.80
Purchase #4	$210.45	4.284%	$219.4657	$219.47	$219.45	$219.50
Purchase #5	$138.47	4.578%	$144.8092	$144.81	$144.80	$144.80
Purchase #6	$224.71	10.180%	$247.5855	$247.59	$247.60	$247.60
Purchase #7	$206.37	8.305%	$223.509	$223.51	$223.50	$223.50
7 purchase totals =	$1,007.19		$1,079.8681	$1,079.88	$1,079.80	$1,079.90