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	$215.53	4.413%	$225.0413	$225.04	$225.05	$225.00
Purchase #2	$32.61	4.210%	$33.9829	$33.98	$34.00	$34.00
Purchase #3	$198.31	7.584%	$213.3498	$213.35	$213.35	$213.30
Purchase #4	$249.55	4.539%	$260.8771	$260.88	$260.90	$260.90
Purchase #5	$32.26	9.272%	$35.2511	$35.25	$35.25	$35.30
Purchase #6	$180.52	8.859%	$196.5123	$196.51	$196.50	$196.50
Purchase #7	$124.74	6.184%	$132.4539	$132.45	$132.45	$132.50
7 purchase totals =	$1,033.52		$1,097.4684	$1,097.46	$1,097.50	$1,097.50