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	$141.79	10.341%	$156.4525	$156.45	$156.45	$156.50
Purchase #2	$221.61	10.444%	$244.7549	$244.75	$244.75	$244.80
Purchase #3	$31.87	3.293%	$32.9195	$32.92	$32.90	$32.90
Purchase #4	$32.93	13.622%	$37.4157	$37.42	$37.40	$37.40
Purchase #5	$172.86	4.574%	$180.7666	$180.77	$180.75	$180.80
Purchase #6	$70.59	9.730%	$77.4584	$77.46	$77.45	$77.50
Purchase #7	$249.36	13.565%	$283.1857	$283.19	$283.20	$283.20
7 purchase totals =	$921.01		$1,012.9533	$1,012.96	$1,012.90	$1,013.10