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	$94.74	5.487%	$99.9384	$99.94	$99.95	$99.90
Purchase #2	$203.32	12.104%	$227.9299	$227.93	$227.95	$227.90
Purchase #3	$247.95	10.607%	$274.2501	$274.25	$274.25	$274.30
Purchase #4	$100.90	7.802%	$108.7722	$108.77	$108.75	$108.80
Purchase #5	$99.60	3.377%	$102.9635	$102.96	$102.95	$103.00
Purchase #6	$168.32	8.557%	$182.7231	$182.72	$182.70	$182.70
Purchase #7	$131.99	9.481%	$144.504	$144.50	$144.50	$144.50
7 purchase totals =	$1,046.82		$1,141.0812	$1,141.07	$1,141.05	$1,141.10