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	$159.84	8.266%	$173.0524	$173.05	$173.05	$173.10
Purchase #2	$177.79	3.762%	$184.4785	$184.48	$184.50	$184.50
Purchase #3	$62.88	10.616%	$69.5553	$69.56	$69.55	$69.60
Purchase #4	$90.59	9.308%	$99.0221	$99.02	$99.00	$99.00
Purchase #5	$166.74	3.156%	$172.0023	$172.00	$172.00	$172.00
Purchase #6	$151.91	4.553%	$158.8265	$158.83	$158.85	$158.80
Purchase #7	$57.78	12.333%	$64.906	$64.91	$64.90	$64.90
7 purchase totals =	$867.53		$921.8431	$921.85	$921.85	$921.90