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	$197.69	4.118%	$205.8309	$205.83	$205.85	$205.80
Purchase #2	$247.91	4.308%	$258.59	$258.59	$258.60	$258.60
Purchase #3	$5.98	13.604%	$6.7935	$6.79	$6.80	$6.80
Purchase #4	$182.76	4.431%	$190.8581	$190.86	$190.85	$190.90
Purchase #5	$92.37	8.644%	$100.3545	$100.35	$100.35	$100.40
Purchase #6	$66.39	4.175%	$69.1618	$69.16	$69.15	$69.20
Purchase #7	$67.63	3.321%	$69.876	$69.88	$69.90	$69.90
7 purchase totals =	$860.73		$901.4648	$901.46	$901.50	$901.60