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	$213.57	4.365%	$222.8923	$222.89	$222.90	$222.90
Purchase #2	$236.37	13.664%	$268.6676	$268.67	$268.65	$268.70
Purchase #3	$36.83	5.738%	$38.9433	$38.94	$38.95	$38.90
Purchase #4	$233.31	9.351%	$255.1268	$255.13	$255.15	$255.10
Purchase #5	$104.85	9.214%	$114.5109	$114.51	$114.50	$114.50
Purchase #6	$183.42	3.231%	$189.3463	$189.35	$189.35	$189.30
Purchase #7	$186.29	13.195%	$210.871	$210.87	$210.85	$210.90
7 purchase totals =	$1,194.64		$1,300.3582	$1,300.36	$1,300.35	$1,300.30