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	$222.39	5.155%	$233.8542	$233.85	$233.85	$233.90
Purchase #2	$142.45	10.649%	$157.6195	$157.62	$157.60	$157.60
Purchase #3	$169.88	10.446%	$187.6257	$187.63	$187.65	$187.60
Purchase #4	$185.93	5.755%	$196.6303	$196.63	$196.65	$196.60
Purchase #5	$112.96	7.486%	$121.4162	$121.42	$121.40	$121.40
Purchase #6	$74.45	13.513%	$84.5104	$84.51	$84.50	$84.50
Purchase #7	$53.90	13.597%	$61.2288	$61.23	$61.25	$61.20
7 purchase totals =	$961.96		$1,042.8851	$1,042.89	$1,042.90	$1,042.80