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	$98.67	3.846%	$102.4648	$102.46	$102.45	$102.50
Purchase #2	$152.62	7.617%	$164.2451	$164.25	$164.25	$164.20
Purchase #3	$122.65	4.839%	$128.585	$128.59	$128.60	$128.60
Purchase #4	$114.28	5.407%	$120.4591	$120.46	$120.45	$120.50
Purchase #5	$229.91	8.273%	$248.9305	$248.93	$248.95	$248.90
Purchase #6	$245.27	8.395%	$265.8604	$265.86	$265.85	$265.90
Purchase #7	$59.96	10.787%	$66.4279	$66.43	$66.45	$66.40
7 purchase totals =	$1,023.36		$1,096.9728	$1,096.98	$1,097.00	$1,097.00