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	$84.94	4.791%	$89.0095	$89.01	$89.00	$89.00
Purchase #2	$171.97	8.609%	$186.7749	$186.77	$186.75	$186.80
Purchase #3	$143.88	3.218%	$148.5101	$148.51	$148.50	$148.50
Purchase #4	$126.69	3.342%	$130.924	$130.92	$130.90	$130.90
Purchase #5	$137.72	11.323%	$153.314	$153.31	$153.30	$153.30
Purchase #6	$249.77	9.564%	$273.658	$273.66	$273.65	$273.70
Purchase #7	$77.52	5.833%	$82.0417	$82.04	$82.05	$82.00
7 purchase totals =	$992.49		$1,064.2322	$1,064.22	$1,064.15	$1,064.20