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	$179.45	3.191%	$185.1762	$185.18	$185.20	$185.20
Purchase #2	$130.86	13.182%	$148.11	$148.11	$148.10	$148.10
Purchase #3	$133.98	8.130%	$144.8726	$144.87	$144.85	$144.90
Purchase #4	$229.34	10.545%	$253.5239	$253.52	$253.50	$253.50
Purchase #5	$68.73	5.449%	$72.4751	$72.48	$72.50	$72.50
Purchase #6	$95.27	3.707%	$98.8017	$98.80	$98.80	$98.80
Purchase #7	$238.72	10.644%	$264.1294	$264.13	$264.15	$264.10
7 purchase totals =	$1,076.35		$1,167.0889	$1,167.09	$1,167.10	$1,167.10