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	$216.42	9.754%	$237.5296	$237.53	$237.55	$237.50
Purchase #2	$19.82	7.116%	$21.2304	$21.23	$21.25	$21.20
Purchase #3	$26.56	6.468%	$28.2779	$28.28	$28.30	$28.30
Purchase #4	$94.86	9.547%	$103.9163	$103.92	$103.90	$103.90
Purchase #5	$92.39	7.791%	$99.5881	$99.59	$99.60	$99.60
Purchase #6	$95.50	3.185%	$98.5417	$98.54	$98.55	$98.50
Purchase #7	$106.61	4.841%	$111.771	$111.77	$111.75	$111.80
7 purchase totals =	$652.16		$700.8550	$700.86	$700.90	$700.80