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	$82.87	12.178%	$92.9619	$92.96	$92.95	$93.00
Purchase #2	$176.27	13.793%	$200.5829	$200.58	$200.60	$200.60
Purchase #3	$84.32	3.195%	$87.014	$87.01	$87.00	$87.00
Purchase #4	$43.31	13.649%	$49.2214	$49.22	$49.20	$49.20
Purchase #5	$161.95	12.311%	$181.8877	$181.89	$181.90	$181.90
Purchase #6	$45.34	7.141%	$48.5777	$48.58	$48.60	$48.60
Purchase #7	$80.53	11.624%	$89.8908	$89.89	$89.90	$89.90
7 purchase totals =	$674.59		$750.1364	$750.13	$750.15	$750.20