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	$134.48	10.726%	$148.9043	$148.90	$148.90	$148.90
Purchase #2	$46.47	3.121%	$47.9203	$47.92	$47.90	$47.90
Purchase #3	$108.67	10.347%	$119.9141	$119.91	$119.90	$119.90
Purchase #4	$72.40	5.788%	$76.5905	$76.59	$76.60	$76.60
Purchase #5	$207.89	5.260%	$218.825	$218.83	$218.85	$218.80
Purchase #6	$208.66	6.425%	$222.0664	$222.07	$222.05	$222.10
Purchase #7	$215.75	6.277%	$229.2926	$229.29	$229.30	$229.30
7 purchase totals =	$994.32		$1,063.5132	$1,063.51	$1,063.50	$1,063.50