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	$41.65	6.303%	$44.2752	$44.28	$44.30	$44.30
Purchase #2	$92.89	8.234%	$100.5386	$100.54	$100.55	$100.50
Purchase #3	$136.63	6.252%	$145.1721	$145.17	$145.15	$145.20
Purchase #4	$200.82	12.675%	$226.2739	$226.27	$226.25	$226.30
Purchase #5	$215.34	3.506%	$222.8898	$222.89	$222.90	$222.90
Purchase #6	$98.58	5.346%	$103.8501	$103.85	$103.85	$103.90
Purchase #7	$207.81	6.455%	$221.2241	$221.22	$221.20	$221.20
7 purchase totals =	$993.72		$1,064.2238	$1,064.22	$1,064.20	$1,064.30