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	$175.93	11.866%	$196.8059	$196.81	$196.80	$196.80
Purchase #2	$173.50	10.398%	$191.5405	$191.54	$191.55	$191.50
Purchase #3	$137.83	10.559%	$152.3835	$152.38	$152.40	$152.40
Purchase #4	$198.37	10.290%	$218.7823	$218.78	$218.80	$218.80
Purchase #5	$17.56	11.571%	$19.5919	$19.59	$19.60	$19.60
Purchase #6	$136.55	4.541%	$142.7507	$142.75	$142.75	$142.80
Purchase #7	$98.53	13.370%	$111.7035	$111.70	$111.70	$111.70
7 purchase totals =	$938.27		$1,033.5583	$1,033.55	$1,033.60	$1,033.60