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	$81.27	13.392%	$92.1537	$92.15	$92.15	$92.20
Purchase #2	$158.53	13.208%	$179.4686	$179.47	$179.45	$179.50
Purchase #3	$119.82	13.584%	$136.0963	$136.10	$136.10	$136.10
Purchase #4	$59.72	3.323%	$61.7045	$61.70	$61.70	$61.70
Purchase #5	$170.49	5.180%	$179.3214	$179.32	$179.30	$179.30
Purchase #6	$171.71	8.537%	$186.3689	$186.37	$186.35	$186.40
Purchase #7	$244.78	8.337%	$265.1873	$265.19	$265.20	$265.20
7 purchase totals =	$1,006.32		$1,100.3007	$1,100.30	$1,100.25	$1,100.40