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	$86.94	10.279%	$95.8766	$95.88	$95.90	$95.90
Purchase #2	$127.63	12.353%	$143.3961	$143.40	$143.40	$143.40
Purchase #3	$191.98	13.496%	$217.8896	$217.89	$217.90	$217.90
Purchase #4	$120.94	5.336%	$127.3934	$127.39	$127.40	$127.40
Purchase #5	$213.98	13.270%	$242.3751	$242.38	$242.40	$242.40
Purchase #6	$92.49	7.404%	$99.338	$99.34	$99.35	$99.30
Purchase #7	$15.47	11.218%	$17.2054	$17.21	$17.20	$17.20
7 purchase totals =	$849.43		$943.4742	$943.49	$943.55	$943.50