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	$177.27	12.209%	$198.9129	$198.91	$198.90	$198.90
Purchase #2	$144.66	6.791%	$154.4839	$154.48	$154.50	$154.50
Purchase #3	$175.85	13.635%	$199.8271	$199.83	$199.85	$199.80
Purchase #4	$7.55	9.256%	$8.2488	$8.25	$8.25	$8.20
Purchase #5	$143.67	8.294%	$155.586	$155.59	$155.60	$155.60
Purchase #6	$201.49	6.529%	$214.6453	$214.65	$214.65	$214.60
Purchase #7	$175.61	11.689%	$196.1371	$196.14	$196.15	$196.10
7 purchase totals =	$1,026.10		$1,127.8411	$1,127.85	$1,127.90	$1,127.70