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	$91.39	5.183%	$96.1267	$96.13	$96.15	$96.10
Purchase #2	$32.69	9.569%	$35.8181	$35.82	$35.80	$35.80
Purchase #3	$77.87	5.381%	$82.0602	$82.06	$82.05	$82.10
Purchase #4	$117.98	10.670%	$130.5685	$130.57	$130.55	$130.60
Purchase #5	$217.83	10.604%	$240.9287	$240.93	$240.95	$240.90
Purchase #6	$43.41	11.677%	$48.479	$48.48	$48.50	$48.50
Purchase #7	$204.60	10.810%	$226.7173	$226.72	$226.70	$226.70
7 purchase totals =	$785.77		$860.6985	$860.71	$860.70	$860.70