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	$85.73	11.108%	$95.2529	$95.25	$95.25	$95.30
Purchase #2	$34.31	4.845%	$35.9723	$35.97	$35.95	$36.00
Purchase #3	$85.51	5.159%	$89.9215	$89.92	$89.90	$89.90
Purchase #4	$40.34	3.419%	$41.7192	$41.72	$41.70	$41.70
Purchase #5	$129.60	9.642%	$142.096	$142.10	$142.10	$142.10
Purchase #6	$243.55	9.621%	$266.9819	$266.98	$267.00	$267.00
Purchase #7	$154.77	10.152%	$170.4823	$170.48	$170.50	$170.50
7 purchase totals =	$773.81		$842.4261	$842.42	$842.40	$842.50