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	$67.84	11.863%	$75.8879	$75.89	$75.90	$75.90
Purchase #2	$111.63	11.775%	$124.7744	$124.77	$124.75	$124.80
Purchase #3	$241.55	11.194%	$268.5891	$268.59	$268.60	$268.60
Purchase #4	$40.69	4.818%	$42.6504	$42.65	$42.65	$42.70
Purchase #5	$123.90	6.742%	$132.2533	$132.25	$132.25	$132.30
Purchase #6	$214.98	7.594%	$231.3056	$231.31	$231.30	$231.30
Purchase #7	$151.38	10.419%	$167.1523	$167.15	$167.15	$167.20
7 purchase totals =	$951.97		$1,042.6130	$1,042.61	$1,042.60	$1,042.80