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	$217.73	13.289%	$246.6641	$246.66	$246.65	$246.70
Purchase #2	$93.59	12.832%	$105.5995	$105.60	$105.60	$105.60
Purchase #3	$17.65	10.716%	$19.5414	$19.54	$19.55	$19.50
Purchase #4	$176.27	13.126%	$199.4072	$199.41	$199.40	$199.40
Purchase #5	$92.84	8.594%	$100.8187	$100.82	$100.80	$100.80
Purchase #6	$98.50	11.582%	$109.9083	$109.91	$109.90	$109.90
Purchase #7	$222.70	12.554%	$250.6578	$250.66	$250.65	$250.70
7 purchase totals =	$919.28		$1,032.5970	$1,032.60	$1,032.55	$1,032.60