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	$140.68	4.435%	$146.9192	$146.92	$146.90	$146.90
Purchase #2	$134.75	3.526%	$139.5013	$139.50	$139.50	$139.50
Purchase #3	$81.62	4.291%	$85.1223	$85.12	$85.10	$85.10
Purchase #4	$96.50	4.391%	$100.7373	$100.74	$100.75	$100.70
Purchase #5	$33.41	5.442%	$35.2282	$35.23	$35.25	$35.20
Purchase #6	$98.81	10.377%	$109.0635	$109.06	$109.05	$109.10
Purchase #7	$230.64	10.636%	$255.1709	$255.17	$255.15	$255.20
7 purchase totals =	$816.41		$871.7427	$871.74	$871.70	$871.70