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	$199.96	11.193%	$222.3415	$222.34	$222.35	$222.30
Purchase #2	$63.86	12.440%	$71.8042	$71.80	$71.80	$71.80
Purchase #3	$36.63	10.166%	$40.3538	$40.35	$40.35	$40.40
Purchase #4	$159.80	11.374%	$177.9757	$177.98	$178.00	$178.00
Purchase #5	$228.99	4.330%	$238.9053	$238.91	$238.90	$238.90
Purchase #6	$30.55	6.830%	$32.6366	$32.64	$32.65	$32.60
Purchase #7	$235.38	12.749%	$265.3886	$265.39	$265.40	$265.40
7 purchase totals =	$955.17		$1,049.4057	$1,049.41	$1,049.45	$1,049.40