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	$235.50	3.567%	$243.9003	$243.90	$243.90	$243.90
Purchase #2	$85.86	10.494%	$94.8701	$94.87	$94.85	$94.90
Purchase #3	$116.37	13.409%	$131.9741	$131.97	$131.95	$132.00
Purchase #4	$210.31	13.607%	$238.9269	$238.93	$238.95	$238.90
Purchase #5	$131.56	9.127%	$143.5675	$143.57	$143.55	$143.60
Purchase #6	$206.49	5.384%	$217.6074	$217.61	$217.60	$217.60
Purchase #7	$138.72	3.453%	$143.51	$143.51	$143.50	$143.50
7 purchase totals =	$1,124.81		$1,214.3563	$1,214.36	$1,214.30	$1,214.40