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	$63.30	11.866%	$70.8112	$70.81	$70.80	$70.80
Purchase #2	$83.46	7.669%	$89.8605	$89.86	$89.85	$89.90
Purchase #3	$41.98	4.749%	$43.9736	$43.97	$43.95	$44.00
Purchase #4	$45.32	5.448%	$47.789	$47.79	$47.80	$47.80
Purchase #5	$33.82	10.611%	$37.4086	$37.41	$37.40	$37.40
Purchase #6	$129.68	6.161%	$137.6696	$137.67	$137.65	$137.70
Purchase #7	$89.77	13.361%	$101.7642	$101.76	$101.75	$101.80
7 purchase totals =	$487.33		$529.2767	$529.27	$529.20	$529.40