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	$41.82	3.371%	$43.2298	$43.23	$43.25	$43.20
Purchase #2	$73.47	12.233%	$82.4576	$82.46	$82.45	$82.50
Purchase #3	$62.70	4.214%	$65.3422	$65.34	$65.35	$65.30
Purchase #4	$80.76	12.116%	$90.5449	$90.54	$90.55	$90.50
Purchase #5	$103.94	11.495%	$115.8879	$115.89	$115.90	$115.90
Purchase #6	$113.44	7.266%	$121.6826	$121.68	$121.70	$121.70
Purchase #7	$238.63	7.743%	$257.1071	$257.11	$257.10	$257.10
7 purchase totals =	$714.76		$776.2521	$776.25	$776.30	$776.20