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	$89.54	13.485%	$101.6145	$101.61	$101.60	$101.60
Purchase #2	$177.67	4.863%	$186.3101	$186.31	$186.30	$186.30
Purchase #3	$123.84	6.425%	$131.7967	$131.80	$131.80	$131.80
Purchase #4	$156.73	7.689%	$168.781	$168.78	$168.80	$168.80
Purchase #5	$28.92	8.691%	$31.4334	$31.43	$31.45	$31.40
Purchase #6	$87.37	12.728%	$98.4905	$98.49	$98.50	$98.50
Purchase #7	$69.79	4.553%	$72.9675	$72.97	$72.95	$73.00
7 purchase totals =	$733.86		$791.3937	$791.39	$791.40	$791.40