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	$146.47	3.691%	$151.8762	$151.88	$151.90	$151.90
Purchase #2	$116.41	6.147%	$123.5657	$123.57	$123.55	$123.60
Purchase #3	$168.86	4.483%	$176.43	$176.43	$176.45	$176.40
Purchase #4	$97.53	13.313%	$110.5142	$110.51	$110.50	$110.50
Purchase #5	$39.89	11.473%	$44.4666	$44.47	$44.45	$44.50
Purchase #6	$188.80	3.698%	$195.7818	$195.78	$195.80	$195.80
Purchase #7	$248.50	10.278%	$274.0408	$274.04	$274.05	$274.00
7 purchase totals =	$1,006.46		$1,076.6753	$1,076.68	$1,076.70	$1,076.70