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	$33.45	4.444%	$34.9365	$34.94	$34.95	$34.90
Purchase #2	$43.85	4.846%	$45.975	$45.98	$46.00	$46.00
Purchase #3	$37.42	4.551%	$39.123	$39.12	$39.10	$39.10
Purchase #4	$32.26	3.334%	$33.3355	$33.34	$33.35	$33.30
Purchase #5	$151.64	4.106%	$157.8663	$157.87	$157.85	$157.90
Purchase #6	$121.60	8.506%	$131.9433	$131.94	$131.95	$131.90
Purchase #7	$103.87	12.168%	$116.5089	$116.51	$116.50	$116.50
7 purchase totals =	$524.09		$559.6885	$559.70	$559.70	$559.60