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	$39.85	11.813%	$44.5575	$44.56	$44.55	$44.60
Purchase #2	$93.78	5.369%	$98.815	$98.82	$98.80	$98.80
Purchase #3	$11.25	9.685%	$12.3396	$12.34	$12.35	$12.30
Purchase #4	$147.50	9.139%	$160.98	$160.98	$161.00	$161.00
Purchase #5	$121.80	7.815%	$131.3187	$131.32	$131.30	$131.30
Purchase #6	$51.47	8.653%	$55.9237	$55.92	$55.90	$55.90
Purchase #7	$94.27	3.752%	$97.807	$97.81	$97.80	$97.80
7 purchase totals =	$559.92		$601.7415	$601.75	$601.70	$601.70