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	$61.25	8.421%	$66.4079	$66.41	$66.40	$66.40
Purchase #2	$27.55	3.735%	$28.579	$28.58	$28.60	$28.60
Purchase #3	$147.79	3.164%	$152.4661	$152.47	$152.45	$152.50
Purchase #4	$59.73	12.438%	$67.1592	$67.16	$67.15	$67.20
Purchase #5	$57.37	7.801%	$61.8454	$61.85	$61.85	$61.80
Purchase #6	$172.45	5.624%	$182.1486	$182.15	$182.15	$182.10
Purchase #7	$193.88	8.336%	$210.0418	$210.04	$210.05	$210.00
7 purchase totals =	$720.02		$768.6480	$768.66	$768.65	$768.60