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	$38.81	13.323%	$43.9807	$43.98	$44.00	$44.00
Purchase #2	$181.49	8.250%	$196.4629	$196.46	$196.45	$196.50
Purchase #3	$69.67	12.537%	$78.4045	$78.40	$78.40	$78.40
Purchase #4	$13.96	11.229%	$15.5276	$15.53	$15.55	$15.50
Purchase #5	$244.64	10.481%	$270.2807	$270.28	$270.30	$270.30
Purchase #6	$164.87	8.412%	$178.7389	$178.74	$178.75	$178.70
Purchase #7	$96.35	7.666%	$103.7362	$103.74	$103.75	$103.70
7 purchase totals =	$809.79		$887.1315	$887.13	$887.20	$887.10