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	$67.45	11.845%	$75.4395	$75.44	$75.45	$75.40
Purchase #2	$45.30	6.469%	$48.2305	$48.23	$48.25	$48.20
Purchase #3	$109.33	6.779%	$116.7415	$116.74	$116.75	$116.70
Purchase #4	$140.44	7.229%	$150.5924	$150.59	$150.60	$150.60
Purchase #5	$55.67	13.339%	$63.0958	$63.10	$63.10	$63.10
Purchase #6	$94.40	6.273%	$100.3217	$100.32	$100.30	$100.30
Purchase #7	$191.27	9.799%	$210.0125	$210.01	$210.00	$210.00
7 purchase totals =	$703.86		$764.4339	$764.43	$764.45	$764.30