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	$62.90	13.568%	$71.4343	$71.43	$71.45	$71.40
Purchase #2	$74.52	12.384%	$83.7486	$83.75	$83.75	$83.70
Purchase #3	$165.46	6.363%	$175.9882	$175.99	$176.00	$176.00
Purchase #4	$16.38	7.492%	$17.6072	$17.61	$17.60	$17.60
Purchase #5	$55.48	6.508%	$59.0906	$59.09	$59.10	$59.10
Purchase #6	$142.34	7.547%	$153.0824	$153.08	$153.10	$153.10
Purchase #7	$31.71	6.735%	$33.8457	$33.85	$33.85	$33.80
7 purchase totals =	$548.79		$594.7970	$594.80	$594.85	$594.70