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	$36.83	12.643%	$41.4864	$41.49	$41.50	$41.50
Purchase #2	$84.98	5.435%	$89.5987	$89.60	$89.60	$89.60
Purchase #3	$9.33	5.593%	$9.8518	$9.85	$9.85	$9.90
Purchase #4	$132.72	8.861%	$144.4803	$144.48	$144.50	$144.50
Purchase #5	$67.39	13.762%	$76.6642	$76.66	$76.65	$76.70
Purchase #6	$225.62	3.865%	$234.3402	$234.34	$234.35	$234.30
Purchase #7	$171.58	10.480%	$189.5616	$189.56	$189.55	$189.60
7 purchase totals =	$728.45		$785.9832	$785.98	$786.00	$786.10