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	$86.38	7.469%	$92.8317	$92.83	$92.85	$92.80
Purchase #2	$144.82	12.305%	$162.6401	$162.64	$162.65	$162.60
Purchase #3	$54.98	12.622%	$61.9196	$61.92	$61.90	$61.90
Purchase #4	$205.76	8.247%	$222.729	$222.73	$222.75	$222.70
Purchase #5	$136.40	8.800%	$148.4032	$148.40	$148.40	$148.40
Purchase #6	$61.97	11.835%	$69.3041	$69.30	$69.30	$69.30
Purchase #7	$132.73	8.257%	$143.6895	$143.69	$143.70	$143.70
7 purchase totals =	$823.04		$901.5172	$901.51	$901.55	$901.40