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	$22.85	5.830%	$24.1822	$24.18	$24.20	$24.20
Purchase #2	$59.82	12.785%	$67.468	$67.47	$67.45	$67.50
Purchase #3	$37.45	10.270%	$41.2961	$41.30	$41.30	$41.30
Purchase #4	$32.88	13.442%	$37.2997	$37.30	$37.30	$37.30
Purchase #5	$224.83	13.510%	$255.2045	$255.20	$255.20	$255.20
Purchase #6	$150.36	13.566%	$170.7578	$170.76	$170.75	$170.80
Purchase #7	$65.65	8.275%	$71.0825	$71.08	$71.10	$71.10
7 purchase totals =	$593.84		$667.2908	$667.29	$667.30	$667.40