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	$66.38	9.386%	$72.6104	$72.61	$72.60	$72.60
Purchase #2	$60.54	8.372%	$65.6084	$65.61	$65.60	$65.60
Purchase #3	$67.91	11.532%	$75.7414	$75.74	$75.75	$75.70
Purchase #4	$93.90	7.354%	$100.8054	$100.81	$100.80	$100.80
Purchase #5	$66.77	7.678%	$71.8966	$71.90	$71.90	$71.90
Purchase #6	$98.89	13.179%	$111.9227	$111.92	$111.90	$111.90
Purchase #7	$245.25	5.279%	$258.1967	$258.20	$258.20	$258.20
7 purchase totals =	$699.64		$756.7816	$756.79	$756.75	$756.70