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	$244.35	6.842%	$261.0684	$261.07	$261.05	$261.10
Purchase #2	$81.46	4.396%	$85.041	$85.04	$85.05	$85.00
Purchase #3	$9.75	11.468%	$10.8681	$10.87	$10.85	$10.90
Purchase #4	$180.49	5.739%	$190.8483	$190.85	$190.85	$190.80
Purchase #5	$136.67	6.360%	$145.3622	$145.36	$145.35	$145.40
Purchase #6	$65.61	3.209%	$67.7154	$67.72	$67.70	$67.70
Purchase #7	$84.25	6.384%	$89.6285	$89.63	$89.65	$89.60
7 purchase totals =	$802.58		$850.5319	$850.54	$850.50	$850.50