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	$172.41	10.861%	$191.1355	$191.14	$191.15	$191.10
Purchase #2	$185.90	12.550%	$209.2305	$209.23	$209.25	$209.20
Purchase #3	$33.51	12.732%	$37.7765	$37.78	$37.80	$37.80
Purchase #4	$127.28	7.698%	$137.078	$137.08	$137.10	$137.10
Purchase #5	$192.74	7.104%	$206.4322	$206.43	$206.45	$206.40
Purchase #6	$106.31	11.443%	$118.4751	$118.48	$118.50	$118.50
Purchase #7	$76.87	7.447%	$82.5945	$82.59	$82.60	$82.60
7 purchase totals =	$895.02		$982.7223	$982.73	$982.85	$982.70