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	$126.50	4.296%	$131.9344	$131.93	$131.95	$131.90
Purchase #2	$155.84	8.753%	$169.4807	$169.48	$169.50	$169.50
Purchase #3	$107.97	11.711%	$120.6144	$120.61	$120.60	$120.60
Purchase #4	$33.65	4.868%	$35.2881	$35.29	$35.30	$35.30
Purchase #5	$132.40	10.572%	$146.3973	$146.40	$146.40	$146.40
Purchase #6	$33.98	4.546%	$35.5247	$35.52	$35.50	$35.50
Purchase #7	$206.45	4.319%	$215.3666	$215.37	$215.35	$215.40
7 purchase totals =	$796.79		$854.6062	$854.60	$854.60	$854.60