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	$52.67	5.234%	$55.4267	$55.43	$55.45	$55.40
Purchase #2	$243.60	13.255%	$275.8892	$275.89	$275.90	$275.90
Purchase #3	$49.78	13.140%	$56.3211	$56.32	$56.30	$56.30
Purchase #4	$164.38	4.217%	$171.3119	$171.31	$171.30	$171.30
Purchase #5	$175.99	8.643%	$191.2008	$191.20	$191.20	$191.20
Purchase #6	$47.46	12.812%	$53.5406	$53.54	$53.55	$53.50
Purchase #7	$248.78	11.243%	$276.7503	$276.75	$276.75	$276.80
7 purchase totals =	$982.66		$1,080.4406	$1,080.44	$1,080.45	$1,080.40