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	$39.59	10.778%	$43.857	$43.86	$43.85	$43.90
Purchase #2	$14.45	9.820%	$15.869	$15.87	$15.85	$15.90
Purchase #3	$237.90	5.655%	$251.3532	$251.35	$251.35	$251.40
Purchase #4	$174.30	5.591%	$184.0451	$184.05	$184.05	$184.00
Purchase #5	$113.86	12.214%	$127.7669	$127.77	$127.75	$127.80
Purchase #6	$70.74	11.647%	$78.9791	$78.98	$79.00	$79.00
Purchase #7	$27.49	8.240%	$29.7552	$29.76	$29.75	$29.80
7 purchase totals =	$678.33		$731.6255	$731.64	$731.60	$731.80