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	$155.94	4.432%	$162.8513	$162.85	$162.85	$162.90
Purchase #2	$231.88	11.506%	$258.5601	$258.56	$258.55	$258.60
Purchase #3	$188.54	10.318%	$207.9936	$207.99	$208.00	$208.00
Purchase #4	$54.30	3.727%	$56.3238	$56.32	$56.30	$56.30
Purchase #5	$127.89	7.301%	$137.2272	$137.23	$137.25	$137.20
Purchase #6	$137.80	12.373%	$154.85	$154.85	$154.85	$154.90
Purchase #7	$83.98	13.558%	$95.366	$95.37	$95.35	$95.40
7 purchase totals =	$980.33		$1,073.1720	$1,073.17	$1,073.15	$1,073.30