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	$14.37	8.614%	$15.6078	$15.61	$15.60	$15.60
Purchase #2	$31.73	3.576%	$32.8647	$32.86	$32.85	$32.90
Purchase #3	$175.55	8.508%	$190.4858	$190.49	$190.50	$190.50
Purchase #4	$40.40	6.873%	$43.1767	$43.18	$43.20	$43.20
Purchase #5	$78.66	3.432%	$81.3596	$81.36	$81.35	$81.40
Purchase #6	$31.69	5.176%	$33.3303	$33.33	$33.35	$33.30
Purchase #7	$77.54	11.486%	$86.4462	$86.45	$86.45	$86.40
7 purchase totals =	$449.94		$483.2711	$483.28	$483.30	$483.30