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	$101.86	9.570%	$111.608	$111.61	$111.60	$111.60
Purchase #2	$22.36	6.716%	$23.8617	$23.86	$23.85	$23.90
Purchase #3	$125.51	11.374%	$139.7855	$139.79	$139.80	$139.80
Purchase #4	$168.53	13.124%	$190.6479	$190.65	$190.65	$190.60
Purchase #5	$68.60	3.873%	$71.2569	$71.26	$71.25	$71.30
Purchase #6	$219.25	10.558%	$242.3984	$242.40	$242.40	$242.40
Purchase #7	$96.31	7.684%	$103.7105	$103.71	$103.70	$103.70
7 purchase totals =	$802.42		$883.2689	$883.28	$883.25	$883.30