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	$176.66	3.550%	$182.9314	$182.93	$182.95	$182.90
Purchase #2	$103.50	5.216%	$108.8986	$108.90	$108.90	$108.90
Purchase #3	$171.46	12.695%	$193.2268	$193.23	$193.25	$193.20
Purchase #4	$31.45	4.576%	$32.8892	$32.89	$32.90	$32.90
Purchase #5	$241.62	8.195%	$261.4208	$261.42	$261.40	$261.40
Purchase #6	$85.91	4.167%	$89.4899	$89.49	$89.50	$89.50
Purchase #7	$167.50	13.711%	$190.4659	$190.47	$190.45	$190.50
7 purchase totals =	$978.10		$1,059.3226	$1,059.33	$1,059.35	$1,059.30