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	$178.49	9.314%	$195.1146	$195.11	$195.10	$195.10
Purchase #2	$125.81	11.190%	$139.8881	$139.89	$139.90	$139.90
Purchase #3	$92.86	5.855%	$98.297	$98.30	$98.30	$98.30
Purchase #4	$17.86	10.746%	$19.7792	$19.78	$19.80	$19.80
Purchase #5	$133.54	8.337%	$144.6732	$144.67	$144.65	$144.70
Purchase #6	$136.83	10.540%	$151.2519	$151.25	$151.25	$151.30
Purchase #7	$35.83	13.695%	$40.7369	$40.74	$40.75	$40.70
7 purchase totals =	$721.22		$789.7409	$789.74	$789.75	$789.80