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	$83.96	3.462%	$86.8667	$86.87	$86.85	$86.90
Purchase #2	$166.36	12.730%	$187.5376	$187.54	$187.55	$187.50
Purchase #3	$121.42	5.224%	$127.763	$127.76	$127.75	$127.80
Purchase #4	$32.26	10.400%	$35.615	$35.62	$35.60	$35.60
Purchase #5	$97.35	13.291%	$110.2888	$110.29	$110.30	$110.30
Purchase #6	$88.96	11.742%	$99.4057	$99.41	$99.40	$99.40
Purchase #7	$48.64	11.858%	$54.4077	$54.41	$54.40	$54.40
7 purchase totals =	$638.95		$701.8845	$701.90	$701.85	$701.90