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	$232.82	13.314%	$263.8177	$263.82	$263.80	$263.80
Purchase #2	$172.31	4.157%	$179.4729	$179.47	$179.45	$179.50
Purchase #3	$240.66	6.306%	$255.836	$255.84	$255.85	$255.80
Purchase #4	$118.51	3.243%	$122.3533	$122.35	$122.35	$122.40
Purchase #5	$71.59	3.804%	$74.3133	$74.31	$74.30	$74.30
Purchase #6	$170.54	12.159%	$191.276	$191.28	$191.30	$191.30
Purchase #7	$70.49	10.509%	$77.8978	$77.90	$77.90	$77.90
7 purchase totals =	$1,076.92		$1,164.9670	$1,164.97	$1,164.95	$1,165.00