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	$205.83	6.797%	$219.8203	$219.82	$219.80	$219.80
Purchase #2	$83.70	8.142%	$90.5149	$90.51	$90.50	$90.50
Purchase #3	$33.71	5.821%	$35.6723	$35.67	$35.65	$35.70
Purchase #4	$203.26	9.298%	$222.1591	$222.16	$222.15	$222.20
Purchase #5	$207.79	9.328%	$227.1727	$227.17	$227.15	$227.20
Purchase #6	$70.49	9.348%	$77.0794	$77.08	$77.10	$77.10
Purchase #7	$122.33	11.401%	$136.2768	$136.28	$136.30	$136.30
7 purchase totals =	$927.11		$1,008.6955	$1,008.69	$1,008.65	$1,008.80