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	$244.55	3.386%	$252.8305	$252.83	$252.85	$252.80
Purchase #2	$172.85	13.514%	$196.2089	$196.21	$196.20	$196.20
Purchase #3	$67.76	7.346%	$72.7376	$72.74	$72.75	$72.70
Purchase #4	$245.67	12.209%	$275.6639	$275.66	$275.65	$275.70
Purchase #5	$101.45	11.129%	$112.7404	$112.74	$112.75	$112.70
Purchase #6	$128.80	8.440%	$139.6707	$139.67	$139.65	$139.70
Purchase #7	$238.64	13.514%	$270.8898	$270.89	$270.90	$270.90
7 purchase totals =	$1,199.72		$1,320.7418	$1,320.74	$1,320.75	$1,320.70