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	$60.99	7.441%	$65.5283	$65.53	$65.55	$65.50
Purchase #2	$74.97	5.874%	$79.3737	$79.37	$79.35	$79.40
Purchase #3	$144.92	9.625%	$158.8686	$158.87	$158.85	$158.90
Purchase #4	$209.93	11.130%	$233.2952	$233.30	$233.30	$233.30
Purchase #5	$119.56	9.618%	$131.0593	$131.06	$131.05	$131.10
Purchase #6	$221.34	3.229%	$228.4871	$228.49	$228.50	$228.50
Purchase #7	$53.97	10.186%	$59.4674	$59.47	$59.45	$59.50
7 purchase totals =	$885.68		$956.0796	$956.09	$956.05	$956.20