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	$173.96	6.789%	$185.7701	$185.77	$185.75	$185.80
Purchase #2	$87.36	3.736%	$90.6238	$90.62	$90.60	$90.60
Purchase #3	$138.84	7.529%	$149.2933	$149.29	$149.30	$149.30
Purchase #4	$81.37	11.664%	$90.861	$90.86	$90.85	$90.90
Purchase #5	$35.86	7.270%	$38.467	$38.47	$38.45	$38.50
Purchase #6	$103.31	8.425%	$112.0139	$112.01	$112.00	$112.00
Purchase #7	$154.97	6.668%	$165.3034	$165.30	$165.30	$165.30
7 purchase totals =	$775.67		$832.3325	$832.32	$832.25	$832.40