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	$82.79	4.579%	$86.581	$86.58	$86.60	$86.60
Purchase #2	$170.42	7.739%	$183.6088	$183.61	$183.60	$183.60
Purchase #3	$35.56	7.671%	$38.2878	$38.29	$38.30	$38.30
Purchase #4	$152.85	5.262%	$160.893	$160.89	$160.90	$160.90
Purchase #5	$106.61	10.188%	$117.4714	$117.47	$117.45	$117.50
Purchase #6	$180.87	4.365%	$188.765	$188.77	$188.75	$188.80
Purchase #7	$219.35	11.519%	$244.6169	$244.62	$244.60	$244.60
7 purchase totals =	$948.45		$1,020.2239	$1,020.23	$1,020.20	$1,020.30