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	$43.41	9.471%	$47.5214	$47.52	$47.50	$47.50
Purchase #2	$135.50	13.841%	$154.2546	$154.25	$154.25	$154.30
Purchase #3	$170.70	4.462%	$178.3166	$178.32	$178.30	$178.30
Purchase #4	$96.56	4.551%	$100.9544	$100.95	$100.95	$101.00
Purchase #5	$187.80	9.197%	$205.072	$205.07	$205.05	$205.10
Purchase #6	$111.39	13.134%	$126.02	$126.02	$126.00	$126.00
Purchase #7	$40.33	5.439%	$42.5235	$42.52	$42.50	$42.50
7 purchase totals =	$785.69		$854.6625	$854.65	$854.55	$854.70