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	$174.65	3.582%	$180.906	$180.91	$180.90	$180.90
Purchase #2	$37.47	7.536%	$40.2937	$40.29	$40.30	$40.30
Purchase #3	$211.26	11.283%	$235.0965	$235.10	$235.10	$235.10
Purchase #4	$155.83	5.268%	$164.0391	$164.04	$164.05	$164.00
Purchase #5	$95.48	8.321%	$103.4249	$103.42	$103.40	$103.40
Purchase #6	$103.47	12.291%	$116.1875	$116.19	$116.20	$116.20
Purchase #7	$29.42	10.551%	$32.5241	$32.52	$32.50	$32.50
7 purchase totals =	$807.58		$872.4718	$872.47	$872.45	$872.40