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	$176.43	5.129%	$185.4791	$185.48	$185.50	$185.50
Purchase #2	$148.62	5.595%	$156.9353	$156.94	$156.95	$156.90
Purchase #3	$85.50	6.293%	$90.8805	$90.88	$90.90	$90.90
Purchase #4	$138.39	3.304%	$142.9624	$142.96	$142.95	$143.00
Purchase #5	$90.95	7.679%	$97.9341	$97.93	$97.95	$97.90
Purchase #6	$242.76	3.179%	$250.4773	$250.48	$250.50	$250.50
Purchase #7	$100.73	7.178%	$107.9604	$107.96	$107.95	$108.00
7 purchase totals =	$983.38		$1,032.6291	$1,032.63	$1,032.70	$1,032.70