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	$68.37	6.670%	$72.9303	$72.93	$72.95	$72.90
Purchase #2	$110.85	7.361%	$119.0097	$119.01	$119.00	$119.00
Purchase #3	$221.75	4.331%	$231.354	$231.35	$231.35	$231.40
Purchase #4	$72.56	9.570%	$79.504	$79.50	$79.50	$79.50
Purchase #5	$146.72	13.528%	$166.5683	$166.57	$166.55	$166.60
Purchase #6	$237.91	7.534%	$255.8341	$255.83	$255.85	$255.80
Purchase #7	$40.80	4.786%	$42.7527	$42.75	$42.75	$42.80
7 purchase totals =	$898.96		$967.9531	$967.94	$967.95	$968.00