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	$189.51	5.397%	$199.7379	$199.74	$199.75	$199.70
Purchase #2	$139.32	3.303%	$143.9217	$143.92	$143.90	$143.90
Purchase #3	$204.33	11.508%	$227.8443	$227.84	$227.85	$227.80
Purchase #4	$106.53	4.547%	$111.3739	$111.37	$111.35	$111.40
Purchase #5	$145.92	8.459%	$158.2634	$158.26	$158.25	$158.30
Purchase #6	$65.50	11.590%	$73.0915	$73.09	$73.10	$73.10
Purchase #7	$84.50	8.591%	$91.7594	$91.76	$91.75	$91.80
7 purchase totals =	$935.61		$1,005.9921	$1,005.98	$1,005.95	$1,006.00