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	$186.46	3.112%	$192.2626	$192.26	$192.25	$192.30
Purchase #2	$92.66	8.461%	$100.5	$100.50	$100.50	$100.50
Purchase #3	$51.83	6.800%	$55.3544	$55.35	$55.35	$55.40
Purchase #4	$232.27	12.587%	$261.5058	$261.51	$261.50	$261.50
Purchase #5	$239.38	3.583%	$247.957	$247.96	$247.95	$248.00
Purchase #6	$51.64	5.778%	$54.6238	$54.62	$54.60	$54.60
Purchase #7	$123.36	6.173%	$130.975	$130.98	$131.00	$131.00
7 purchase totals =	$977.60		$1,043.1786	$1,043.18	$1,043.15	$1,043.30