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	$141.70	13.282%	$160.5206	$160.52	$160.50	$160.50
Purchase #2	$224.66	4.601%	$234.9966	$235.00	$235.00	$235.00
Purchase #3	$232.38	4.524%	$242.8929	$242.89	$242.90	$242.90
Purchase #4	$38.26	5.435%	$40.3394	$40.34	$40.35	$40.30
Purchase #5	$191.81	9.819%	$210.6438	$210.64	$210.65	$210.60
Purchase #6	$152.68	13.223%	$172.8689	$172.87	$172.85	$172.90
Purchase #7	$40.34	8.128%	$43.6188	$43.62	$43.60	$43.60
7 purchase totals =	$1,021.83		$1,105.8810	$1,105.88	$1,105.85	$1,105.80