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	$45.68	12.329%	$51.3119	$51.31	$51.30	$51.30
Purchase #2	$145.97	12.383%	$164.0455	$164.05	$164.05	$164.00
Purchase #3	$94.52	12.799%	$106.6176	$106.62	$106.60	$106.60
Purchase #4	$206.91	7.451%	$222.3269	$222.33	$222.35	$222.30
Purchase #5	$207.93	12.243%	$233.3869	$233.39	$233.40	$233.40
Purchase #6	$169.55	12.614%	$190.937	$190.94	$190.95	$190.90
Purchase #7	$188.42	5.850%	$199.4426	$199.44	$199.45	$199.40
7 purchase totals =	$1,058.98		$1,168.0684	$1,168.08	$1,168.10	$1,167.90