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	$151.78	11.206%	$168.7885	$168.79	$168.80	$168.80
Purchase #2	$67.25	10.151%	$74.0765	$74.08	$74.10	$74.10
Purchase #3	$242.40	8.131%	$262.1095	$262.11	$262.10	$262.10
Purchase #4	$94.47	6.129%	$100.2601	$100.26	$100.25	$100.30
Purchase #5	$29.38	3.447%	$30.3927	$30.39	$30.40	$30.40
Purchase #6	$51.52	8.589%	$55.9451	$55.95	$55.95	$55.90
Purchase #7	$12.58	10.485%	$13.899	$13.90	$13.90	$13.90
7 purchase totals =	$649.38		$705.4714	$705.48	$705.50	$705.50