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	$84.42	12.133%	$94.6627	$94.66	$94.65	$94.70
Purchase #2	$98.66	10.607%	$109.1249	$109.12	$109.10	$109.10
Purchase #3	$91.88	8.707%	$99.88	$99.88	$99.90	$99.90
Purchase #4	$76.63	3.142%	$79.0377	$79.04	$79.05	$79.00
Purchase #5	$132.61	8.690%	$144.1338	$144.13	$144.15	$144.10
Purchase #6	$45.68	5.116%	$48.017	$48.02	$48.00	$48.00
Purchase #7	$170.47	8.714%	$185.3248	$185.32	$185.30	$185.30
7 purchase totals =	$700.35		$760.1809	$760.17	$760.15	$760.10