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	$114.28	11.545%	$127.4736	$127.47	$127.45	$127.50
Purchase #2	$80.53	3.220%	$83.1231	$83.12	$83.10	$83.10
Purchase #3	$36.78	12.874%	$41.5151	$41.52	$41.50	$41.50
Purchase #4	$241.58	7.817%	$260.4643	$260.46	$260.45	$260.50
Purchase #5	$42.59	4.317%	$44.4286	$44.43	$44.45	$44.40
Purchase #6	$72.27	7.835%	$77.9324	$77.93	$77.95	$77.90
Purchase #7	$21.96	4.622%	$22.975	$22.98	$23.00	$23.00
7 purchase totals =	$609.99		$657.9121	$657.91	$657.90	$657.90