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	$94.60	11.856%	$105.8158	$105.82	$105.80	$105.80
Purchase #2	$96.32	13.149%	$108.9851	$108.99	$109.00	$109.00
Purchase #3	$123.50	4.789%	$129.4144	$129.41	$129.40	$129.40
Purchase #4	$169.97	5.586%	$179.4645	$179.46	$179.45	$179.50
Purchase #5	$215.33	9.561%	$235.9177	$235.92	$235.90	$235.90
Purchase #6	$188.64	4.311%	$196.7723	$196.77	$196.75	$196.80
Purchase #7	$151.86	4.663%	$158.9412	$158.94	$158.95	$158.90
7 purchase totals =	$1,040.22		$1,115.3110	$1,115.31	$1,115.25	$1,115.30