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	$44.72	10.526%	$49.4272	$49.43	$49.45	$49.40
Purchase #2	$238.57	7.541%	$256.5606	$256.56	$256.55	$256.60
Purchase #3	$137.80	3.364%	$142.4356	$142.44	$142.45	$142.40
Purchase #4	$127.54	5.526%	$134.5879	$134.59	$134.60	$134.60
Purchase #5	$196.45	11.767%	$219.5663	$219.57	$219.55	$219.60
Purchase #6	$156.85	13.702%	$178.3416	$178.34	$178.35	$178.30
Purchase #7	$76.91	3.409%	$79.5319	$79.53	$79.55	$79.50
7 purchase totals =	$978.84		$1,060.4511	$1,060.46	$1,060.50	$1,060.40