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	$184.55	6.596%	$196.7229	$196.72	$196.70	$196.70
Purchase #2	$228.85	8.746%	$248.8652	$248.87	$248.85	$248.90
Purchase #3	$220.42	5.148%	$231.7672	$231.77	$231.75	$231.80
Purchase #4	$240.57	6.194%	$255.4709	$255.47	$255.45	$255.50
Purchase #5	$99.36	12.790%	$112.0681	$112.07	$112.05	$112.10
Purchase #6	$48.49	12.449%	$54.5265	$54.53	$54.55	$54.50
Purchase #7	$224.66	3.806%	$233.2106	$233.21	$233.20	$233.20
7 purchase totals =	$1,246.90		$1,332.6314	$1,332.64	$1,332.55	$1,332.70