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	$95.92	10.527%	$106.0175	$106.02	$106.00	$106.00
Purchase #2	$17.90	4.123%	$18.638	$18.64	$18.65	$18.60
Purchase #3	$90.56	11.348%	$100.8367	$100.84	$100.85	$100.80
Purchase #4	$22.46	6.743%	$23.9745	$23.97	$23.95	$24.00
Purchase #5	$93.32	7.176%	$100.0166	$100.02	$100.00	$100.00
Purchase #6	$73.36	7.549%	$78.8979	$78.90	$78.90	$78.90
Purchase #7	$124.81	3.250%	$128.8663	$128.87	$128.85	$128.90
7 purchase totals =	$518.33		$557.2475	$557.26	$557.20	$557.20