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	$211.25	5.190%	$222.2139	$222.21	$222.20	$222.20
Purchase #2	$157.25	4.299%	$164.0102	$164.01	$164.00	$164.00
Purchase #3	$43.60	13.793%	$49.6137	$49.61	$49.60	$49.60
Purchase #4	$164.33	6.363%	$174.7863	$174.79	$174.80	$174.80
Purchase #5	$198.77	8.443%	$215.5522	$215.55	$215.55	$215.60
Purchase #6	$72.43	7.869%	$78.1295	$78.13	$78.15	$78.10
Purchase #7	$130.43	3.475%	$134.9624	$134.96	$134.95	$135.00
7 purchase totals =	$978.06		$1,039.2682	$1,039.26	$1,039.25	$1,039.30