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	$236.85	13.839%	$269.6277	$269.63	$269.65	$269.60
Purchase #2	$89.59	8.710%	$97.3933	$97.39	$97.40	$97.40
Purchase #3	$53.51	9.526%	$58.6074	$58.61	$58.60	$58.60
Purchase #4	$124.73	10.250%	$137.5148	$137.51	$137.50	$137.50
Purchase #5	$214.68	3.695%	$222.6124	$222.61	$222.60	$222.60
Purchase #6	$20.98	4.497%	$21.9235	$21.92	$21.90	$21.90
Purchase #7	$225.53	12.599%	$253.9445	$253.94	$253.95	$253.90
7 purchase totals =	$965.87		$1,061.6236	$1,061.61	$1,061.60	$1,061.50