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	$40.93	5.312%	$43.1042	$43.10	$43.10	$43.10
Purchase #2	$131.42	10.546%	$145.2796	$145.28	$145.30	$145.30
Purchase #3	$199.87	13.579%	$227.0103	$227.01	$227.00	$227.00
Purchase #4	$41.27	13.293%	$46.756	$46.76	$46.75	$46.80
Purchase #5	$139.58	9.801%	$153.2602	$153.26	$153.25	$153.30
Purchase #6	$99.84	9.593%	$109.4177	$109.42	$109.40	$109.40
Purchase #7	$198.54	5.406%	$209.2731	$209.27	$209.25	$209.30
7 purchase totals =	$851.45		$934.1011	$934.10	$934.05	$934.20