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	$84.43	7.702%	$90.9328	$90.93	$90.95	$90.90
Purchase #2	$182.48	3.716%	$189.261	$189.26	$189.25	$189.30
Purchase #3	$49.54	12.412%	$55.6889	$55.69	$55.70	$55.70
Purchase #4	$50.83	10.598%	$56.217	$56.22	$56.20	$56.20
Purchase #5	$185.77	12.686%	$209.3368	$209.34	$209.35	$209.30
Purchase #6	$12.83	5.534%	$13.54	$13.54	$13.55	$13.50
Purchase #7	$164.60	5.778%	$174.1106	$174.11	$174.10	$174.10
7 purchase totals =	$730.48		$789.0871	$789.09	$789.10	$789.00