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	$160.42	9.421%	$175.5332	$175.53	$175.55	$175.50
Purchase #2	$184.74	8.286%	$200.0476	$200.05	$200.05	$200.00
Purchase #3	$62.78	13.821%	$71.4568	$71.46	$71.45	$71.50
Purchase #4	$193.52	11.693%	$216.1483	$216.15	$216.15	$216.10
Purchase #5	$180.67	8.715%	$196.4154	$196.42	$196.40	$196.40
Purchase #6	$169.47	3.742%	$175.8116	$175.81	$175.80	$175.80
Purchase #7	$28.41	5.536%	$29.9828	$29.98	$30.00	$30.00
7 purchase totals =	$980.01		$1,065.3957	$1,065.40	$1,065.40	$1,065.30