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	$186.53	7.692%	$200.8779	$200.88	$200.90	$200.90
Purchase #2	$87.41	11.684%	$97.623	$97.62	$97.60	$97.60
Purchase #3	$60.77	12.102%	$68.1244	$68.12	$68.10	$68.10
Purchase #4	$248.84	9.376%	$272.1712	$272.17	$272.15	$272.20
Purchase #5	$81.89	7.377%	$87.931	$87.93	$87.95	$87.90
Purchase #6	$181.88	8.193%	$196.7814	$196.78	$196.80	$196.80
Purchase #7	$154.78	6.191%	$164.3624	$164.36	$164.35	$164.40
7 purchase totals =	$1,002.10		$1,087.8713	$1,087.86	$1,087.85	$1,087.90