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	$40.50	12.840%	$45.7002	$45.70	$45.70	$45.70
Purchase #2	$207.83	8.458%	$225.4083	$225.41	$225.40	$225.40
Purchase #3	$47.47	8.289%	$51.4048	$51.40	$51.40	$51.40
Purchase #4	$195.88	13.831%	$222.9722	$222.97	$222.95	$223.00
Purchase #5	$41.59	12.150%	$46.6432	$46.64	$46.65	$46.60
Purchase #6	$241.48	7.640%	$259.9291	$259.93	$259.95	$259.90
Purchase #7	$163.37	9.832%	$179.4325	$179.43	$179.45	$179.40
7 purchase totals =	$938.12		$1,031.4903	$1,031.48	$1,031.50	$1,031.40