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	$126.53	7.761%	$136.35	$136.35	$136.35	$136.40
Purchase #2	$189.35	13.398%	$214.7191	$214.72	$214.70	$214.70
Purchase #3	$195.85	12.540%	$220.4096	$220.41	$220.40	$220.40
Purchase #4	$31.42	12.839%	$35.454	$35.45	$35.45	$35.50
Purchase #5	$169.45	11.398%	$188.7639	$188.76	$188.75	$188.80
Purchase #6	$105.50	5.681%	$111.4935	$111.49	$111.50	$111.50
Purchase #7	$43.70	6.336%	$46.4688	$46.47	$46.45	$46.50
7 purchase totals =	$861.80		$953.6589	$953.65	$953.60	$953.80