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	$98.84	12.640%	$111.3334	$111.33	$111.35	$111.30
Purchase #2	$73.80	3.190%	$76.1542	$76.15	$76.15	$76.20
Purchase #3	$129.49	9.266%	$141.4885	$141.49	$141.50	$141.50
Purchase #4	$195.50	4.280%	$203.8674	$203.87	$203.85	$203.90
Purchase #5	$63.84	13.470%	$72.4392	$72.44	$72.45	$72.40
Purchase #6	$245.53	4.319%	$256.1344	$256.13	$256.15	$256.10
Purchase #7	$186.98	11.314%	$208.1349	$208.13	$208.15	$208.10
7 purchase totals =	$993.98		$1,069.5520	$1,069.54	$1,069.60	$1,069.50