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	$63.46	12.176%	$71.1869	$71.19	$71.20	$71.20
Purchase #2	$92.28	8.861%	$100.4569	$100.46	$100.45	$100.50
Purchase #3	$27.50	5.395%	$28.9836	$28.98	$29.00	$29.00
Purchase #4	$127.86	10.303%	$141.0334	$141.03	$141.05	$141.00
Purchase #5	$178.59	3.662%	$185.13	$185.13	$185.15	$185.10
Purchase #6	$186.88	4.386%	$195.0766	$195.08	$195.10	$195.10
Purchase #7	$98.65	4.570%	$103.1583	$103.16	$103.15	$103.20
7 purchase totals =	$775.22		$825.0257	$825.03	$825.10	$825.10