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	$26.62	3.572%	$27.5709	$27.57	$27.55	$27.60
Purchase #2	$86.82	6.809%	$92.7316	$92.73	$92.75	$92.70
Purchase #3	$12.46	11.534%	$13.8971	$13.90	$13.90	$13.90
Purchase #4	$146.46	6.671%	$156.2303	$156.23	$156.25	$156.20
Purchase #5	$201.31	10.556%	$222.5603	$222.56	$222.55	$222.60
Purchase #6	$69.55	12.847%	$78.4851	$78.49	$78.50	$78.50
Purchase #7	$99.47	5.446%	$104.8871	$104.89	$104.90	$104.90
7 purchase totals =	$642.69		$696.3624	$696.37	$696.40	$696.40