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	$85.90	7.623%	$92.4482	$92.45	$92.45	$92.40
Purchase #2	$173.81	3.488%	$179.8725	$179.87	$179.85	$179.90
Purchase #3	$44.65	4.119%	$46.4891	$46.49	$46.50	$46.50
Purchase #4	$37.98	4.770%	$39.7916	$39.79	$39.80	$39.80
Purchase #5	$123.86	3.291%	$127.9362	$127.94	$127.95	$127.90
Purchase #6	$12.98	11.484%	$14.4706	$14.47	$14.45	$14.50
Purchase #7	$118.73	12.789%	$133.9144	$133.91	$133.90	$133.90
7 purchase totals =	$597.91		$634.9226	$634.92	$634.90	$634.90