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	$35.60	13.370%	$40.3597	$40.36	$40.35	$40.40
Purchase #2	$17.92	9.149%	$19.5595	$19.56	$19.55	$19.60
Purchase #3	$171.38	7.308%	$183.9045	$183.90	$183.90	$183.90
Purchase #4	$37.26	13.541%	$42.3054	$42.31	$42.30	$42.30
Purchase #5	$45.98	6.277%	$48.8662	$48.87	$48.85	$48.90
Purchase #6	$86.54	9.521%	$94.7795	$94.78	$94.80	$94.80
Purchase #7	$29.54	10.223%	$32.5599	$32.56	$32.55	$32.60
7 purchase totals =	$424.22		$462.3347	$462.34	$462.30	$462.50