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	$143.60	3.404%	$148.4881	$148.49	$148.50	$148.50
Purchase #2	$85.31	6.151%	$90.5574	$90.56	$90.55	$90.60
Purchase #3	$148.97	7.797%	$160.5852	$160.59	$160.60	$160.60
Purchase #4	$199.66	11.591%	$222.8026	$222.80	$222.80	$222.80
Purchase #5	$133.72	7.599%	$143.8814	$143.88	$143.90	$143.90
Purchase #6	$28.78	4.440%	$30.0578	$30.06	$30.05	$30.10
Purchase #7	$211.63	10.815%	$234.5178	$234.52	$234.50	$234.50
7 purchase totals =	$951.67		$1,030.8903	$1,030.90	$1,030.90	$1,031.00