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	$119.50	4.321%	$124.6636	$124.66	$124.65	$124.70
Purchase #2	$32.61	8.218%	$35.2899	$35.29	$35.30	$35.30
Purchase #3	$76.66	7.843%	$82.6724	$82.67	$82.65	$82.70
Purchase #4	$46.29	5.574%	$48.8702	$48.87	$48.85	$48.90
Purchase #5	$55.45	12.807%	$62.5515	$62.55	$62.55	$62.60
Purchase #6	$104.94	3.417%	$108.5258	$108.53	$108.55	$108.50
Purchase #7	$63.32	11.380%	$70.5258	$70.53	$70.55	$70.50
7 purchase totals =	$498.77		$533.0992	$533.10	$533.10	$533.20