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	$187.67	4.756%	$196.5956	$196.60	$196.60	$196.60
Purchase #2	$147.92	13.413%	$167.7605	$167.76	$167.75	$167.80
Purchase #3	$186.55	13.385%	$211.5197	$211.52	$211.50	$211.50
Purchase #4	$220.73	5.660%	$233.2233	$233.22	$233.20	$233.20
Purchase #5	$117.34	5.314%	$123.5754	$123.58	$123.60	$123.60
Purchase #6	$58.47	8.506%	$63.4435	$63.44	$63.45	$63.40
Purchase #7	$242.49	7.335%	$260.2766	$260.28	$260.30	$260.30
7 purchase totals =	$1,161.17		$1,256.3946	$1,256.40	$1,256.40	$1,256.40