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	$150.72	4.392%	$157.3396	$157.34	$157.35	$157.30
Purchase #2	$177.91	8.611%	$193.2298	$193.23	$193.25	$193.20
Purchase #3	$66.27	9.567%	$72.6101	$72.61	$72.60	$72.60
Purchase #4	$192.45	11.605%	$214.7838	$214.78	$214.80	$214.80
Purchase #5	$125.58	13.180%	$142.1314	$142.13	$142.15	$142.10
Purchase #6	$28.33	7.648%	$30.4967	$30.50	$30.50	$30.50
Purchase #7	$192.50	4.368%	$200.9084	$200.91	$200.90	$200.90
7 purchase totals =	$933.76		$1,011.4998	$1,011.50	$1,011.55	$1,011.40