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	$205.38	4.738%	$215.1109	$215.11	$215.10	$215.10
Purchase #2	$135.89	5.301%	$143.0935	$143.09	$143.10	$143.10
Purchase #3	$91.33	5.690%	$96.5267	$96.53	$96.55	$96.50
Purchase #4	$206.74	9.135%	$225.6257	$225.63	$225.65	$225.60
Purchase #5	$169.67	10.431%	$187.3683	$187.37	$187.35	$187.40
Purchase #6	$59.83	11.468%	$66.6913	$66.69	$66.70	$66.70
Purchase #7	$131.62	9.205%	$143.7356	$143.74	$143.75	$143.70
7 purchase totals =	$1,000.46		$1,078.1520	$1,078.16	$1,078.20	$1,078.10