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	$57.52	3.156%	$59.3353	$59.34	$59.35	$59.30
Purchase #2	$106.52	13.237%	$120.6201	$120.62	$120.60	$120.60
Purchase #3	$185.44	5.392%	$195.4389	$195.44	$195.45	$195.40
Purchase #4	$71.47	11.402%	$79.619	$79.62	$79.60	$79.60
Purchase #5	$11.96	13.252%	$13.5449	$13.54	$13.55	$13.50
Purchase #6	$113.72	3.341%	$117.5194	$117.52	$117.50	$117.50
Purchase #7	$79.38	8.823%	$86.3837	$86.38	$86.40	$86.40
7 purchase totals =	$626.01		$672.4613	$672.46	$672.45	$672.30