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	$9.41	6.421%	$10.0142	$10.01	$10.00	$10.00
Purchase #2	$64.83	6.225%	$68.8657	$68.87	$68.85	$68.90
Purchase #3	$218.61	13.790%	$248.7563	$248.76	$248.75	$248.80
Purchase #4	$234.38	4.475%	$244.8685	$244.87	$244.85	$244.90
Purchase #5	$240.54	8.701%	$261.4694	$261.47	$261.45	$261.50
Purchase #6	$114.87	7.109%	$123.0361	$123.04	$123.05	$123.00
Purchase #7	$126.53	10.208%	$139.4462	$139.45	$139.45	$139.40
7 purchase totals =	$1,009.17		$1,096.4564	$1,096.47	$1,096.40	$1,096.50