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	$48.61	7.765%	$52.3846	$52.38	$52.40	$52.40
Purchase #2	$207.29	7.765%	$223.3861	$223.39	$223.40	$223.40
Purchase #3	$39.90	11.343%	$44.4259	$44.43	$44.45	$44.40
Purchase #4	$180.34	10.251%	$198.8267	$198.83	$198.85	$198.80
Purchase #5	$29.63	11.517%	$33.0425	$33.04	$33.05	$33.00
Purchase #6	$136.57	3.393%	$141.2038	$141.20	$141.20	$141.20
Purchase #7	$27.54	13.681%	$31.3077	$31.31	$31.30	$31.30
7 purchase totals =	$669.88		$724.5773	$724.58	$724.65	$724.50