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	$136.56	9.334%	$149.3065	$149.31	$149.30	$149.30
Purchase #2	$142.43	5.317%	$150.003	$150.00	$150.00	$150.00
Purchase #3	$43.56	7.617%	$46.878	$46.88	$46.90	$46.90
Purchase #4	$235.32	10.447%	$259.9039	$259.90	$259.90	$259.90
Purchase #5	$89.27	6.854%	$95.3886	$95.39	$95.40	$95.40
Purchase #6	$213.88	11.414%	$238.2923	$238.29	$238.30	$238.30
Purchase #7	$60.63	12.534%	$68.2294	$68.23	$68.25	$68.20
7 purchase totals =	$921.65		$1,008.0017	$1,008.00	$1,008.05	$1,008.00