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	$123.61	3.200%	$127.5655	$127.57	$127.55	$127.60
Purchase #2	$150.52	11.291%	$167.5152	$167.52	$167.50	$167.50
Purchase #3	$69.55	13.597%	$79.0067	$79.01	$79.00	$79.00
Purchase #4	$49.79	10.239%	$54.888	$54.89	$54.90	$54.90
Purchase #5	$91.47	13.787%	$104.081	$104.08	$104.10	$104.10
Purchase #6	$226.61	6.226%	$240.7187	$240.72	$240.70	$240.70
Purchase #7	$150.43	12.838%	$169.7422	$169.74	$169.75	$169.70
7 purchase totals =	$861.98		$943.5173	$943.53	$943.50	$943.50