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	$91.90	8.625%	$99.8264	$99.83	$99.85	$99.80
Purchase #2	$131.45	13.285%	$148.9131	$148.91	$148.90	$148.90
Purchase #3	$69.58	9.815%	$76.4093	$76.41	$76.40	$76.40
Purchase #4	$200.29	7.518%	$215.3478	$215.35	$215.35	$215.30
Purchase #5	$163.26	6.538%	$173.9339	$173.93	$173.95	$173.90
Purchase #6	$237.69	9.687%	$260.715	$260.72	$260.70	$260.70
Purchase #7	$29.86	6.808%	$31.8929	$31.89	$31.90	$31.90
7 purchase totals =	$924.03		$1,007.0384	$1,007.04	$1,007.05	$1,006.90