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	$88.44	10.411%	$97.6475	$97.65	$97.65	$97.60
Purchase #2	$76.62	9.393%	$83.8169	$83.82	$83.80	$83.80
Purchase #3	$95.64	9.196%	$104.4351	$104.44	$104.45	$104.40
Purchase #4	$121.88	4.639%	$127.534	$127.53	$127.55	$127.50
Purchase #5	$28.68	10.356%	$31.6501	$31.65	$31.65	$31.70
Purchase #6	$59.46	3.317%	$61.4323	$61.43	$61.45	$61.40
Purchase #7	$196.72	10.838%	$218.0405	$218.04	$218.05	$218.00
7 purchase totals =	$667.44		$724.5564	$724.56	$724.60	$724.40