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	$37.32	11.248%	$41.5178	$41.52	$41.50	$41.50
Purchase #2	$167.52	11.134%	$186.1717	$186.17	$186.15	$186.20
Purchase #3	$79.72	4.503%	$83.3098	$83.31	$83.30	$83.30
Purchase #4	$96.31	7.138%	$103.1846	$103.18	$103.20	$103.20
Purchase #5	$228.91	7.778%	$246.7146	$246.71	$246.70	$246.70
Purchase #6	$80.40	7.288%	$86.2596	$86.26	$86.25	$86.30
Purchase #7	$91.86	8.831%	$99.9722	$99.97	$99.95	$100.00
7 purchase totals =	$782.04		$847.1303	$847.12	$847.05	$847.20