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	$134.30	5.446%	$141.614	$141.61	$141.60	$141.60
Purchase #2	$185.90	10.406%	$205.2448	$205.24	$205.25	$205.20
Purchase #3	$225.48	10.510%	$249.1779	$249.18	$249.20	$249.20
Purchase #4	$248.94	3.166%	$256.8214	$256.82	$256.80	$256.80
Purchase #5	$127.41	12.210%	$142.9668	$142.97	$142.95	$143.00
Purchase #6	$78.73	6.434%	$83.7955	$83.80	$83.80	$83.80
Purchase #7	$98.53	3.440%	$101.9194	$101.92	$101.90	$101.90
7 purchase totals =	$1,099.29		$1,181.5398	$1,181.54	$1,181.50	$1,181.50