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	$140.46	5.713%	$148.4845	$148.48	$148.50	$148.50
Purchase #2	$54.77	6.523%	$58.3426	$58.34	$58.35	$58.30
Purchase #3	$64.96	12.206%	$72.889	$72.89	$72.90	$72.90
Purchase #4	$46.63	3.804%	$48.4038	$48.40	$48.40	$48.40
Purchase #5	$54.44	4.619%	$56.9546	$56.95	$56.95	$57.00
Purchase #6	$156.45	11.150%	$173.8942	$173.89	$173.90	$173.90
Purchase #7	$14.31	5.535%	$15.1021	$15.10	$15.10	$15.10
7 purchase totals =	$532.02		$574.0708	$574.05	$574.10	$574.10