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	$173.87	8.844%	$189.2471	$189.25	$189.25	$189.20
Purchase #2	$61.66	7.582%	$66.3351	$66.34	$66.35	$66.30
Purchase #3	$228.57	4.539%	$238.9448	$238.94	$238.95	$238.90
Purchase #4	$190.91	8.585%	$207.2996	$207.30	$207.30	$207.30
Purchase #5	$55.86	6.485%	$59.4825	$59.48	$59.50	$59.50
Purchase #6	$161.92	6.397%	$172.278	$172.28	$172.30	$172.30
Purchase #7	$60.90	12.527%	$68.5289	$68.53	$68.55	$68.50
7 purchase totals =	$933.69		$1,002.1160	$1,002.12	$1,002.20	$1,002.00