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	$38.73	6.195%	$41.1293	$41.13	$41.15	$41.10
Purchase #2	$145.32	5.187%	$152.8577	$152.86	$152.85	$152.90
Purchase #3	$213.36	3.532%	$220.8959	$220.90	$220.90	$220.90
Purchase #4	$88.45	13.350%	$100.2581	$100.26	$100.25	$100.30
Purchase #5	$184.55	6.446%	$196.4461	$196.45	$196.45	$196.40
Purchase #6	$142.38	4.178%	$148.3286	$148.33	$148.35	$148.30
Purchase #7	$25.62	9.288%	$27.9996	$28.00	$28.00	$28.00
7 purchase totals =	$838.41		$887.9153	$887.93	$887.95	$887.90