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	$205.91	11.500%	$229.5897	$229.59	$229.60	$229.60
Purchase #2	$197.56	12.863%	$222.9721	$222.97	$222.95	$223.00
Purchase #3	$200.93	9.445%	$219.9078	$219.91	$219.90	$219.90
Purchase #4	$207.25	9.334%	$226.5947	$226.59	$226.60	$226.60
Purchase #5	$78.82	6.221%	$83.7234	$83.72	$83.70	$83.70
Purchase #6	$57.36	7.248%	$61.5175	$61.52	$61.50	$61.50
Purchase #7	$177.49	3.147%	$183.0756	$183.08	$183.10	$183.10
7 purchase totals =	$1,125.32		$1,227.3808	$1,227.38	$1,227.35	$1,227.40