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	$183.59	3.633%	$190.2598	$190.26	$190.25	$190.30
Purchase #2	$172.48	9.202%	$188.3516	$188.35	$188.35	$188.40
Purchase #3	$94.77	5.403%	$99.8904	$99.89	$99.90	$99.90
Purchase #4	$123.46	12.497%	$138.8888	$138.89	$138.90	$138.90
Purchase #5	$174.40	9.533%	$191.0256	$191.03	$191.05	$191.00
Purchase #6	$25.75	10.758%	$28.5202	$28.52	$28.50	$28.50
Purchase #7	$225.29	6.380%	$239.6635	$239.66	$239.65	$239.70
7 purchase totals =	$999.74		$1,076.5999	$1,076.60	$1,076.60	$1,076.70