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	$171.40	12.367%	$192.597	$192.60	$192.60	$192.60
Purchase #2	$28.94	13.568%	$32.8666	$32.87	$32.85	$32.90
Purchase #3	$77.76	11.218%	$86.4831	$86.48	$86.50	$86.50
Purchase #4	$110.73	11.609%	$123.5846	$123.58	$123.60	$123.60
Purchase #5	$229.80	12.540%	$258.6169	$258.62	$258.60	$258.60
Purchase #6	$194.40	10.497%	$214.8062	$214.81	$214.80	$214.80
Purchase #7	$156.81	13.293%	$177.6548	$177.65	$177.65	$177.70
7 purchase totals =	$969.84		$1,086.6092	$1,086.61	$1,086.60	$1,086.70