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	$68.56	11.654%	$76.55	$76.55	$76.55	$76.60
Purchase #2	$50.51	6.651%	$53.8694	$53.87	$53.85	$53.90
Purchase #3	$134.71	6.506%	$143.4742	$143.47	$143.45	$143.50
Purchase #4	$241.43	11.804%	$269.9284	$269.93	$269.95	$269.90
Purchase #5	$126.60	5.416%	$133.4567	$133.46	$133.45	$133.50
Purchase #6	$111.93	11.629%	$124.9463	$124.95	$124.95	$124.90
Purchase #7	$157.94	11.385%	$175.9215	$175.92	$175.90	$175.90
7 purchase totals =	$891.68		$978.1465	$978.15	$978.10	$978.20