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	$93.38	7.564%	$100.4433	$100.44	$100.45	$100.40
Purchase #2	$127.95	13.149%	$144.7741	$144.77	$144.75	$144.80
Purchase #3	$33.81	10.504%	$37.3614	$37.36	$37.35	$37.40
Purchase #4	$69.97	12.258%	$78.5469	$78.55	$78.55	$78.50
Purchase #5	$158.41	6.745%	$169.0948	$169.09	$169.10	$169.10
Purchase #6	$49.46	10.224%	$54.5168	$54.52	$54.50	$54.50
Purchase #7	$131.82	6.235%	$140.039	$140.04	$140.05	$140.00
7 purchase totals =	$664.80		$724.7763	$724.77	$724.75	$724.70