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	$88.34	8.670%	$95.9991	$96.00	$96.00	$96.00
Purchase #2	$197.51	6.553%	$210.4528	$210.45	$210.45	$210.50
Purchase #3	$93.58	8.470%	$101.5062	$101.51	$101.50	$101.50
Purchase #4	$41.74	9.677%	$45.7792	$45.78	$45.80	$45.80
Purchase #5	$71.63	6.716%	$76.4407	$76.44	$76.45	$76.40
Purchase #6	$152.60	13.295%	$172.8882	$172.89	$172.90	$172.90
Purchase #7	$87.51	12.456%	$98.4102	$98.41	$98.40	$98.40
7 purchase totals =	$732.91		$801.4764	$801.48	$801.50	$801.50