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	$35.97	12.218%	$40.3648	$40.36	$40.35	$40.40
Purchase #2	$12.72	9.168%	$13.8862	$13.89	$13.90	$13.90
Purchase #3	$226.98	6.718%	$242.2285	$242.23	$242.25	$242.20
Purchase #4	$234.40	3.580%	$242.7915	$242.79	$242.80	$242.80
Purchase #5	$191.92	9.749%	$210.6303	$210.63	$210.65	$210.60
Purchase #6	$175.62	4.672%	$183.825	$183.83	$183.85	$183.80
Purchase #7	$136.37	8.645%	$148.1592	$148.16	$148.15	$148.20
7 purchase totals =	$1,013.98		$1,081.8855	$1,081.89	$1,081.95	$1,081.90