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	$101.77	3.217%	$105.0439	$105.04	$105.05	$105.00
Purchase #2	$168.71	9.844%	$185.3178	$185.32	$185.30	$185.30
Purchase #3	$46.78	3.355%	$48.3495	$48.35	$48.35	$48.30
Purchase #4	$52.76	12.783%	$59.5043	$59.50	$59.50	$59.50
Purchase #5	$141.90	8.802%	$154.39	$154.39	$154.40	$154.40
Purchase #6	$74.37	10.768%	$82.3782	$82.38	$82.40	$82.40
Purchase #7	$58.34	13.693%	$66.3285	$66.33	$66.35	$66.30
7 purchase totals =	$644.63		$701.3122	$701.31	$701.35	$701.20