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	$42.37	6.406%	$45.0842	$45.08	$45.10	$45.10
Purchase #2	$168.61	11.867%	$188.6189	$188.62	$188.60	$188.60
Purchase #3	$104.98	10.671%	$116.1824	$116.18	$116.20	$116.20
Purchase #4	$23.81	7.269%	$25.5407	$25.54	$25.55	$25.50
Purchase #5	$84.41	3.610%	$87.4572	$87.46	$87.45	$87.50
Purchase #6	$95.37	5.653%	$100.7613	$100.76	$100.75	$100.80
Purchase #7	$180.31	3.270%	$186.2061	$186.21	$186.20	$186.20
7 purchase totals =	$699.86		$749.8508	$749.85	$749.85	$749.90