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	$229.42	4.180%	$239.0098	$239.01	$239.00	$239.00
Purchase #2	$205.48	13.833%	$233.904	$233.90	$233.90	$233.90
Purchase #3	$167.81	7.634%	$180.6206	$180.62	$180.60	$180.60
Purchase #4	$24.31	12.157%	$27.2654	$27.27	$27.25	$27.30
Purchase #5	$166.86	9.385%	$182.5198	$182.52	$182.50	$182.50
Purchase #6	$16.28	12.529%	$18.3197	$18.32	$18.30	$18.30
Purchase #7	$145.66	11.515%	$162.4327	$162.43	$162.45	$162.40
7 purchase totals =	$955.82		$1,044.0720	$1,044.07	$1,044.00	$1,044.00