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	$234.69	13.175%	$265.6104	$265.61	$265.60	$265.60
Purchase #2	$100.76	12.502%	$113.357	$113.36	$113.35	$113.40
Purchase #3	$167.32	3.617%	$173.372	$173.37	$173.35	$173.40
Purchase #4	$150.72	6.132%	$159.9622	$159.96	$159.95	$160.00
Purchase #5	$139.73	3.624%	$144.7938	$144.79	$144.80	$144.80
Purchase #6	$85.67	12.214%	$96.1337	$96.13	$96.15	$96.10
Purchase #7	$82.93	7.863%	$89.4508	$89.45	$89.45	$89.50
7 purchase totals =	$961.82		$1,042.6799	$1,042.67	$1,042.65	$1,042.80