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	$211.96	13.666%	$240.9265	$240.93	$240.95	$240.90
Purchase #2	$128.97	10.213%	$142.1417	$142.14	$142.15	$142.10
Purchase #3	$96.41	3.569%	$99.8509	$99.85	$99.85	$99.90
Purchase #4	$84.78	11.606%	$94.6196	$94.62	$94.60	$94.60
Purchase #5	$200.41	5.213%	$210.8574	$210.86	$210.85	$210.90
Purchase #6	$97.78	11.696%	$109.2163	$109.22	$109.20	$109.20
Purchase #7	$58.54	6.279%	$62.2157	$62.22	$62.20	$62.20
7 purchase totals =	$878.85		$959.8281	$959.84	$959.80	$959.80