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	$211.77	9.260%	$231.3799	$231.38	$231.40	$231.40
Purchase #2	$74.25	5.663%	$78.4548	$78.45	$78.45	$78.50
Purchase #3	$225.25	4.868%	$236.2152	$236.22	$236.20	$236.20
Purchase #4	$214.75	6.832%	$229.4217	$229.42	$229.40	$229.40
Purchase #5	$43.43	4.520%	$45.393	$45.39	$45.40	$45.40
Purchase #6	$82.64	13.118%	$93.4807	$93.48	$93.50	$93.50
Purchase #7	$61.80	11.585%	$68.9595	$68.96	$68.95	$69.00
7 purchase totals =	$913.89		$983.3048	$983.30	$983.30	$983.40