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	$65.75	10.205%	$72.4598	$72.46	$72.45	$72.50
Purchase #2	$113.25	4.505%	$118.3519	$118.35	$118.35	$118.40
Purchase #3	$40.35	3.671%	$41.8312	$41.83	$41.85	$41.80
Purchase #4	$104.83	13.402%	$118.8793	$118.88	$118.90	$118.90
Purchase #5	$99.82	13.465%	$113.2608	$113.26	$113.25	$113.30
Purchase #6	$110.93	8.329%	$120.1694	$120.17	$120.15	$120.20
Purchase #7	$160.38	12.362%	$180.2062	$180.21	$180.20	$180.20
7 purchase totals =	$695.31		$765.1586	$765.16	$765.15	$765.30