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	$184.90	13.614%	$210.0723	$210.07	$210.05	$210.10
Purchase #2	$57.54	10.183%	$63.3993	$63.40	$63.40	$63.40
Purchase #3	$35.72	13.783%	$40.6433	$40.64	$40.65	$40.60
Purchase #4	$139.83	3.288%	$144.4276	$144.43	$144.45	$144.40
Purchase #5	$168.27	5.148%	$176.9325	$176.93	$176.95	$176.90
Purchase #6	$164.37	5.613%	$173.5961	$173.60	$173.60	$173.60
Purchase #7	$94.60	8.254%	$102.4083	$102.41	$102.40	$102.40
7 purchase totals =	$845.23		$911.4794	$911.48	$911.50	$911.40