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	$226.89	12.280%	$254.7521	$254.75	$254.75	$254.80
Purchase #2	$182.37	4.345%	$190.294	$190.29	$190.30	$190.30
Purchase #3	$98.59	13.555%	$111.9539	$111.95	$111.95	$112.00
Purchase #4	$26.72	10.546%	$29.5379	$29.54	$29.55	$29.50
Purchase #5	$109.38	4.389%	$114.1807	$114.18	$114.20	$114.20
Purchase #6	$161.58	10.213%	$178.0822	$178.08	$178.10	$178.10
Purchase #7	$160.78	9.357%	$175.8242	$175.82	$175.80	$175.80
7 purchase totals =	$966.31		$1,054.6250	$1,054.61	$1,054.65	$1,054.70