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	$156.90	12.774%	$176.9424	$176.94	$176.95	$176.90
Purchase #2	$208.64	7.465%	$224.215	$224.22	$224.20	$224.20
Purchase #3	$73.90	11.440%	$82.3542	$82.35	$82.35	$82.40
Purchase #4	$47.81	13.120%	$54.0827	$54.08	$54.10	$54.10
Purchase #5	$159.70	12.315%	$179.3671	$179.37	$179.35	$179.40
Purchase #6	$231.32	5.830%	$244.806	$244.81	$244.80	$244.80
Purchase #7	$65.89	8.228%	$71.3114	$71.31	$71.30	$71.30
7 purchase totals =	$944.16		$1,033.0788	$1,033.08	$1,033.05	$1,033.10