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	$134.69	10.273%	$148.5267	$148.53	$148.55	$148.50
Purchase #2	$219.47	3.729%	$227.654	$227.65	$227.65	$227.70
Purchase #3	$28.75	12.690%	$32.3984	$32.40	$32.40	$32.40
Purchase #4	$245.54	8.870%	$267.3194	$267.32	$267.30	$267.30
Purchase #5	$148.48	10.233%	$163.674	$163.67	$163.65	$163.70
Purchase #6	$59.47	11.609%	$66.3739	$66.37	$66.35	$66.40
Purchase #7	$183.34	3.697%	$190.1181	$190.12	$190.10	$190.10
7 purchase totals =	$1,019.74		$1,096.0645	$1,096.06	$1,096.00	$1,096.10