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	$207.45	13.359%	$235.1632	$235.16	$235.15	$235.20
Purchase #2	$225.70	9.158%	$246.3696	$246.37	$246.35	$246.40
Purchase #3	$198.70	5.633%	$209.8928	$209.89	$209.90	$209.90
Purchase #4	$20.88	7.301%	$22.4044	$22.40	$22.40	$22.40
Purchase #5	$84.38	7.688%	$90.8671	$90.87	$90.85	$90.90
Purchase #6	$16.87	7.762%	$18.1794	$18.18	$18.20	$18.20
Purchase #7	$186.84	5.217%	$196.5874	$196.59	$196.60	$196.60
7 purchase totals =	$940.82		$1,019.4639	$1,019.46	$1,019.45	$1,019.60