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	$186.52	10.830%	$206.7201	$206.72	$206.70	$206.70
Purchase #2	$176.90	13.322%	$200.4666	$200.47	$200.45	$200.50
Purchase #3	$215.34	13.259%	$243.8919	$243.89	$243.90	$243.90
Purchase #4	$30.92	11.458%	$34.4628	$34.46	$34.45	$34.50
Purchase #5	$67.78	5.375%	$71.4232	$71.42	$71.40	$71.40
Purchase #6	$182.81	5.704%	$193.2375	$193.24	$193.25	$193.20
Purchase #7	$138.67	6.375%	$147.5102	$147.51	$147.50	$147.50
7 purchase totals =	$998.94		$1,097.7123	$1,097.71	$1,097.65	$1,097.70