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	$213.39	6.316%	$226.8677	$226.87	$226.85	$226.90
Purchase #2	$234.92	6.386%	$249.922	$249.92	$249.90	$249.90
Purchase #3	$74.75	3.552%	$77.4051	$77.41	$77.40	$77.40
Purchase #4	$160.34	12.216%	$179.9271	$179.93	$179.95	$179.90
Purchase #5	$38.86	3.804%	$40.3382	$40.34	$40.35	$40.30
Purchase #6	$225.49	7.282%	$241.9102	$241.91	$241.90	$241.90
Purchase #7	$95.32	5.162%	$100.2404	$100.24	$100.25	$100.20
7 purchase totals =	$1,043.07		$1,116.6107	$1,116.62	$1,116.60	$1,116.50