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	$96.43	10.731%	$106.7779	$106.78	$106.80	$106.80
Purchase #2	$152.27	13.678%	$173.0975	$173.10	$173.10	$173.10
Purchase #3	$40.43	8.623%	$43.9163	$43.92	$43.90	$43.90
Purchase #4	$78.35	9.476%	$85.7744	$85.77	$85.75	$85.80
Purchase #5	$176.80	3.466%	$182.9279	$182.93	$182.95	$182.90
Purchase #6	$134.90	4.527%	$141.0069	$141.01	$141.00	$141.00
Purchase #7	$33.86	6.182%	$35.9532	$35.95	$35.95	$36.00
7 purchase totals =	$713.04		$769.4541	$769.46	$769.45	$769.50