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	$109.89	8.165%	$118.8625	$118.86	$118.85	$118.90
Purchase #2	$40.30	12.371%	$45.2855	$45.29	$45.30	$45.30
Purchase #3	$101.61	11.462%	$113.2565	$113.26	$113.25	$113.30
Purchase #4	$148.89	12.166%	$167.004	$167.00	$167.00	$167.00
Purchase #5	$126.62	4.687%	$132.5547	$132.55	$132.55	$132.60
Purchase #6	$181.62	4.634%	$190.0363	$190.04	$190.05	$190.00
Purchase #7	$154.66	7.527%	$166.3013	$166.30	$166.30	$166.30
7 purchase totals =	$863.59		$933.3008	$933.30	$933.30	$933.40