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	$106.52	5.571%	$112.4542	$112.45	$112.45	$112.50
Purchase #2	$59.25	3.292%	$61.2005	$61.20	$61.20	$61.20
Purchase #3	$48.28	8.860%	$52.5576	$52.56	$52.55	$52.60
Purchase #4	$56.43	9.823%	$61.9731	$61.97	$61.95	$62.00
Purchase #5	$41.94	9.147%	$45.7763	$45.78	$45.80	$45.80
Purchase #6	$186.26	11.681%	$208.017	$208.02	$208.00	$208.00
Purchase #7	$131.98	7.843%	$142.3312	$142.33	$142.35	$142.30
7 purchase totals =	$630.66		$684.3099	$684.31	$684.30	$684.40