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	$67.49	6.713%	$72.0206	$72.02	$72.00	$72.00
Purchase #2	$234.59	8.864%	$255.3841	$255.38	$255.40	$255.40
Purchase #3	$95.82	9.379%	$104.807	$104.81	$104.80	$104.80
Purchase #4	$158.93	10.499%	$175.6161	$175.62	$175.60	$175.60
Purchase #5	$234.46	12.307%	$263.315	$263.32	$263.30	$263.30
Purchase #6	$195.89	10.277%	$216.0216	$216.02	$216.00	$216.00
Purchase #7	$212.64	3.605%	$220.3057	$220.31	$220.30	$220.30
7 purchase totals =	$1,199.82		$1,307.4701	$1,307.48	$1,307.40	$1,307.40