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	$93.67	7.434%	$100.6334	$100.63	$100.65	$100.60
Purchase #2	$248.58	11.322%	$276.7242	$276.72	$276.70	$276.70
Purchase #3	$114.72	11.475%	$127.8841	$127.88	$127.90	$127.90
Purchase #4	$106.81	3.536%	$110.5868	$110.59	$110.60	$110.60
Purchase #5	$188.72	10.248%	$208.06	$208.06	$208.05	$208.10
Purchase #6	$31.56	12.737%	$35.5798	$35.58	$35.60	$35.60
Purchase #7	$207.82	5.324%	$218.8843	$218.88	$218.90	$218.90
7 purchase totals =	$991.88		$1,078.3526	$1,078.34	$1,078.40	$1,078.40