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	$145.82	10.113%	$160.5668	$160.57	$160.55	$160.60
Purchase #2	$113.89	11.799%	$127.3279	$127.33	$127.35	$127.30
Purchase #3	$116.88	7.342%	$125.4613	$125.46	$125.45	$125.50
Purchase #4	$63.83	13.544%	$72.4751	$72.48	$72.50	$72.50
Purchase #5	$76.77	10.282%	$84.6635	$84.66	$84.65	$84.70
Purchase #6	$30.54	10.309%	$33.6884	$33.69	$33.70	$33.70
Purchase #7	$127.42	9.854%	$139.976	$139.98	$140.00	$140.00
7 purchase totals =	$675.15		$744.1590	$744.17	$744.20	$744.30