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	$31.72	6.738%	$33.8573	$33.86	$33.85	$33.90
Purchase #2	$226.81	12.679%	$255.5672	$255.57	$255.55	$255.60
Purchase #3	$13.35	7.213%	$14.3129	$14.31	$14.30	$14.30
Purchase #4	$236.50	6.409%	$251.6573	$251.66	$251.65	$251.70
Purchase #5	$147.40	7.373%	$158.2678	$158.27	$158.25	$158.30
Purchase #6	$240.39	5.692%	$254.073	$254.07	$254.05	$254.10
Purchase #7	$132.93	8.217%	$143.8529	$143.85	$143.85	$143.90
7 purchase totals =	$1,029.10		$1,111.5884	$1,111.59	$1,111.50	$1,111.80