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	$208.38	3.452%	$215.5733	$215.57	$215.55	$215.60
Purchase #2	$249.59	6.235%	$265.1519	$265.15	$265.15	$265.20
Purchase #3	$135.67	9.746%	$148.8924	$148.89	$148.90	$148.90
Purchase #4	$143.95	9.276%	$157.3028	$157.30	$157.30	$157.30
Purchase #5	$54.56	12.539%	$61.4013	$61.40	$61.40	$61.40
Purchase #6	$83.98	7.382%	$90.1794	$90.18	$90.20	$90.20
Purchase #7	$86.51	10.838%	$95.886	$95.89	$95.90	$95.90
7 purchase totals =	$962.64		$1,034.3871	$1,034.38	$1,034.40	$1,034.50