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	$186.60	12.385%	$209.7104	$209.71	$209.70	$209.70
Purchase #2	$82.97	10.635%	$91.7939	$91.79	$91.80	$91.80
Purchase #3	$66.95	5.734%	$70.7889	$70.79	$70.80	$70.80
Purchase #4	$56.67	4.381%	$59.1527	$59.15	$59.15	$59.20
Purchase #5	$137.86	3.657%	$142.9015	$142.90	$142.90	$142.90
Purchase #6	$207.44	8.359%	$224.7799	$224.78	$224.80	$224.80
Purchase #7	$193.25	6.447%	$205.7088	$205.71	$205.70	$205.70
7 purchase totals =	$931.74		$1,004.8361	$1,004.83	$1,004.85	$1,004.90