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	$78.61	9.689%	$86.2265	$86.23	$86.25	$86.20
Purchase #2	$93.30	8.342%	$101.0831	$101.08	$101.10	$101.10
Purchase #3	$179.53	6.244%	$190.7399	$190.74	$190.75	$190.70
Purchase #4	$79.38	11.339%	$88.3809	$88.38	$88.40	$88.40
Purchase #5	$250.82	3.549%	$259.7216	$259.72	$259.70	$259.70
Purchase #6	$137.87	4.855%	$144.5636	$144.56	$144.55	$144.60
Purchase #7	$126.72	8.529%	$137.5279	$137.53	$137.55	$137.50
7 purchase totals =	$946.23		$1,008.2435	$1,008.24	$1,008.30	$1,008.20