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	$67.96	4.537%	$71.0433	$71.04	$71.05	$71.00
Purchase #2	$109.60	12.548%	$123.3526	$123.35	$123.35	$123.40
Purchase #3	$239.48	7.382%	$257.1584	$257.16	$257.15	$257.20
Purchase #4	$247.96	8.737%	$269.6243	$269.62	$269.60	$269.60
Purchase #5	$32.72	13.318%	$37.0776	$37.08	$37.10	$37.10
Purchase #6	$157.69	5.159%	$165.8252	$165.83	$165.85	$165.80
Purchase #7	$130.33	10.470%	$143.9756	$143.98	$144.00	$144.00
7 purchase totals =	$985.74		$1,068.0570	$1,068.06	$1,068.10	$1,068.10