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	$119.47	3.395%	$123.526	$123.53	$123.55	$123.50
Purchase #2	$115.32	11.594%	$128.6902	$128.69	$128.70	$128.70
Purchase #3	$69.59	13.450%	$78.9499	$78.95	$78.95	$78.90
Purchase #4	$29.54	8.247%	$31.9762	$31.98	$32.00	$32.00
Purchase #5	$73.62	7.507%	$79.1467	$79.15	$79.15	$79.10
Purchase #6	$228.98	13.156%	$259.1046	$259.10	$259.10	$259.10
Purchase #7	$233.31	9.489%	$255.4488	$255.45	$255.45	$255.40
7 purchase totals =	$869.83		$956.8424	$956.85	$956.90	$956.70