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	$30.57	13.277%	$34.6288	$34.63	$34.65	$34.60
Purchase #2	$41.65	6.381%	$44.3077	$44.31	$44.30	$44.30
Purchase #3	$29.96	12.674%	$33.7571	$33.76	$33.75	$33.80
Purchase #4	$169.60	12.143%	$190.1945	$190.19	$190.20	$190.20
Purchase #5	$68.86	5.483%	$72.6356	$72.64	$72.65	$72.60
Purchase #6	$145.95	7.265%	$156.5533	$156.55	$156.55	$156.60
Purchase #7	$40.82	7.551%	$43.9023	$43.90	$43.90	$43.90
7 purchase totals =	$527.41		$575.9793	$575.98	$576.00	$576.00