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	$175.45	13.127%	$198.4813	$198.48	$198.50	$198.50
Purchase #2	$176.44	3.862%	$183.2541	$183.25	$183.25	$183.30
Purchase #3	$150.70	3.721%	$156.3075	$156.31	$156.30	$156.30
Purchase #4	$155.64	9.607%	$170.5923	$170.59	$170.60	$170.60
Purchase #5	$74.55	11.213%	$82.9093	$82.91	$82.90	$82.90
Purchase #6	$20.81	4.546%	$21.756	$21.76	$21.75	$21.80
Purchase #7	$206.37	8.805%	$224.5409	$224.54	$224.55	$224.50
7 purchase totals =	$959.96		$1,037.8414	$1,037.84	$1,037.85	$1,037.90