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	$76.59	11.845%	$85.6621	$85.66	$85.65	$85.70
Purchase #2	$236.33	6.326%	$251.2802	$251.28	$251.30	$251.30
Purchase #3	$37.27	13.513%	$42.3063	$42.31	$42.30	$42.30
Purchase #4	$44.77	7.862%	$48.2898	$48.29	$48.30	$48.30
Purchase #5	$13.46	10.175%	$14.8296	$14.83	$14.85	$14.80
Purchase #6	$118.65	11.303%	$132.061	$132.06	$132.05	$132.10
Purchase #7	$84.29	12.611%	$94.9198	$94.92	$94.90	$94.90
7 purchase totals =	$611.36		$669.3488	$669.35	$669.35	$669.40