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	$98.46	4.623%	$103.0118	$103.01	$103.00	$103.00
Purchase #2	$27.77	6.343%	$29.5315	$29.53	$29.55	$29.50
Purchase #3	$116.37	4.241%	$121.3053	$121.31	$121.30	$121.30
Purchase #4	$35.70	7.735%	$38.4614	$38.46	$38.45	$38.50
Purchase #5	$189.95	3.442%	$196.4881	$196.49	$196.50	$196.50
Purchase #6	$91.86	10.333%	$101.3519	$101.35	$101.35	$101.40
Purchase #7	$41.96	7.112%	$44.9442	$44.94	$44.95	$44.90
7 purchase totals =	$602.07		$635.0942	$635.09	$635.10	$635.10