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	$154.74	7.834%	$166.8623	$166.86	$166.85	$166.90
Purchase #2	$201.59	7.524%	$216.7576	$216.76	$216.75	$216.80
Purchase #3	$79.95	4.565%	$83.5997	$83.60	$83.60	$83.60
Purchase #4	$46.76	3.417%	$48.3578	$48.36	$48.35	$48.40
Purchase #5	$193.42	3.853%	$200.8725	$200.87	$200.85	$200.90
Purchase #6	$143.45	13.146%	$162.3079	$162.31	$162.30	$162.30
Purchase #7	$93.93	10.203%	$103.5137	$103.51	$103.50	$103.50
7 purchase totals =	$913.84		$982.2715	$982.27	$982.20	$982.40