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	$217.89	4.240%	$227.1285	$227.13	$227.15	$227.10
Purchase #2	$62.73	5.811%	$66.3752	$66.38	$66.40	$66.40
Purchase #3	$37.33	12.460%	$41.9813	$41.98	$42.00	$42.00
Purchase #4	$233.26	5.193%	$245.3732	$245.37	$245.35	$245.40
Purchase #5	$100.38	4.141%	$104.5367	$104.54	$104.55	$104.50
Purchase #6	$29.62	12.874%	$33.4333	$33.43	$33.45	$33.40
Purchase #7	$184.76	3.631%	$191.4686	$191.47	$191.45	$191.50
7 purchase totals =	$865.97		$910.2968	$910.30	$910.35	$910.30