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	$5.38	8.143%	$5.8181	$5.82	$5.80	$5.80
Purchase #2	$57.30	7.133%	$61.3872	$61.39	$61.40	$61.40
Purchase #3	$39.40	8.872%	$42.8956	$42.90	$42.90	$42.90
Purchase #4	$101.91	12.739%	$114.8923	$114.89	$114.90	$114.90
Purchase #5	$45.59	13.732%	$51.8504	$51.85	$51.85	$51.90
Purchase #6	$11.34	13.334%	$12.8521	$12.85	$12.85	$12.90
Purchase #7	$116.93	6.596%	$124.6427	$124.64	$124.65	$124.60
7 purchase totals =	$377.85		$414.3384	$414.34	$414.35	$414.40