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	$91.78	9.291%	$100.3073	$100.31	$100.30	$100.30
Purchase #2	$81.86	11.755%	$91.4826	$91.48	$91.50	$91.50
Purchase #3	$207.37	7.707%	$223.352	$223.35	$223.35	$223.40
Purchase #4	$60.52	8.585%	$65.7156	$65.72	$65.70	$65.70
Purchase #5	$142.55	9.346%	$155.8727	$155.87	$155.85	$155.90
Purchase #6	$198.88	9.358%	$217.4912	$217.49	$217.50	$217.50
Purchase #7	$149.96	12.193%	$168.2446	$168.24	$168.25	$168.20
7 purchase totals =	$932.92		$1,022.4660	$1,022.46	$1,022.45	$1,022.50