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	$139.43	8.385%	$151.1212	$151.12	$151.10	$151.10
Purchase #2	$74.85	13.655%	$85.0708	$85.07	$85.05	$85.10
Purchase #3	$203.70	6.748%	$217.4457	$217.45	$217.45	$217.40
Purchase #4	$89.29	5.862%	$94.5242	$94.52	$94.50	$94.50
Purchase #5	$131.56	8.683%	$142.9834	$142.98	$143.00	$143.00
Purchase #6	$91.46	12.518%	$102.909	$102.91	$102.90	$102.90
Purchase #7	$250.29	8.272%	$270.994	$270.99	$271.00	$271.00
7 purchase totals =	$980.58		$1,065.0483	$1,065.04	$1,065.00	$1,065.00