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	$94.71	5.658%	$100.0687	$100.07	$100.05	$100.10
Purchase #2	$231.95	11.180%	$257.882	$257.88	$257.90	$257.90
Purchase #3	$157.80	9.393%	$172.6222	$172.62	$172.60	$172.60
Purchase #4	$47.96	3.820%	$49.7921	$49.79	$49.80	$49.80
Purchase #5	$165.62	9.452%	$181.2744	$181.27	$181.25	$181.30
Purchase #6	$91.68	9.587%	$100.4694	$100.47	$100.45	$100.50
Purchase #7	$177.81	7.652%	$191.416	$191.42	$191.40	$191.40
7 purchase totals =	$967.53		$1,053.5248	$1,053.52	$1,053.45	$1,053.60