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	$117.71	13.704%	$133.841	$133.84	$133.85	$133.80
Purchase #2	$188.45	8.782%	$204.9997	$205.00	$205.00	$205.00
Purchase #3	$92.44	9.856%	$101.5509	$101.55	$101.55	$101.60
Purchase #4	$246.60	13.590%	$280.1129	$280.11	$280.10	$280.10
Purchase #5	$130.86	8.342%	$141.7763	$141.78	$141.80	$141.80
Purchase #6	$38.54	5.516%	$40.6659	$40.67	$40.65	$40.70
Purchase #7	$113.67	12.392%	$127.756	$127.76	$127.75	$127.80
7 purchase totals =	$928.27		$1,030.7027	$1,030.71	$1,030.70	$1,030.80