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	$153.54	10.474%	$169.6218	$169.62	$169.60	$169.60
Purchase #2	$113.79	8.251%	$123.1788	$123.18	$123.20	$123.20
Purchase #3	$114.82	13.616%	$130.4539	$130.45	$130.45	$130.50
Purchase #4	$214.96	12.793%	$242.4598	$242.46	$242.45	$242.50
Purchase #5	$216.42	3.802%	$224.6483	$224.65	$224.65	$224.60
Purchase #6	$38.61	9.723%	$42.3641	$42.36	$42.35	$42.40
Purchase #7	$86.49	10.177%	$95.2921	$95.29	$95.30	$95.30
7 purchase totals =	$938.63		$1,028.0188	$1,028.01	$1,028.00	$1,028.10