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	$32.61	3.189%	$33.6499	$33.65	$33.65	$33.60
Purchase #2	$156.32	9.801%	$171.6409	$171.64	$171.65	$171.60
Purchase #3	$65.91	12.648%	$74.2463	$74.25	$74.25	$74.20
Purchase #4	$116.85	5.806%	$123.6343	$123.63	$123.65	$123.60
Purchase #5	$181.89	3.871%	$188.931	$188.93	$188.95	$188.90
Purchase #6	$201.78	10.185%	$222.3313	$222.33	$222.35	$222.30
Purchase #7	$180.64	8.763%	$196.4695	$196.47	$196.45	$196.50
7 purchase totals =	$936.00		$1,010.9032	$1,010.90	$1,010.95	$1,010.70