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	$39.82	4.426%	$41.5824	$41.58	$41.60	$41.60
Purchase #2	$109.33	8.520%	$118.6449	$118.64	$118.65	$118.60
Purchase #3	$72.33	12.672%	$81.4957	$81.50	$81.50	$81.50
Purchase #4	$55.97	8.816%	$60.9043	$60.90	$60.90	$60.90
Purchase #5	$204.60	12.228%	$229.6185	$229.62	$229.60	$229.60
Purchase #6	$6.47	8.386%	$7.0126	$7.01	$7.00	$7.00
Purchase #7	$176.91	10.867%	$196.1348	$196.13	$196.15	$196.10
7 purchase totals =	$665.43		$735.3932	$735.38	$735.40	$735.30