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	$68.69	13.801%	$78.1699	$78.17	$78.15	$78.20
Purchase #2	$200.53	7.445%	$215.4595	$215.46	$215.45	$215.50
Purchase #3	$8.47	11.184%	$9.4173	$9.42	$9.40	$9.40
Purchase #4	$220.45	6.181%	$234.076	$234.08	$234.10	$234.10
Purchase #5	$247.78	11.638%	$276.6166	$276.62	$276.60	$276.60
Purchase #6	$158.86	6.277%	$168.8316	$168.83	$168.85	$168.80
Purchase #7	$200.74	4.162%	$209.0948	$209.09	$209.10	$209.10
7 purchase totals =	$1,105.52		$1,191.6657	$1,191.67	$1,191.65	$1,191.70