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	$181.76	13.144%	$205.6505	$205.65	$205.65	$205.70
Purchase #2	$184.89	6.511%	$196.9282	$196.93	$196.95	$196.90
Purchase #3	$174.80	12.649%	$196.9105	$196.91	$196.90	$196.90
Purchase #4	$46.66	9.787%	$51.2266	$51.23	$51.25	$51.20
Purchase #5	$129.60	3.769%	$134.4846	$134.48	$134.50	$134.50
Purchase #6	$209.48	9.249%	$228.8548	$228.85	$228.85	$228.90
Purchase #7	$234.47	12.573%	$263.9499	$263.95	$263.95	$263.90
7 purchase totals =	$1,161.66		$1,278.0051	$1,278.00	$1,278.05	$1,278.00