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	$73.40	9.837%	$80.6204	$80.62	$80.60	$80.60
Purchase #2	$86.40	9.460%	$94.5734	$94.57	$94.55	$94.60
Purchase #3	$183.80	6.852%	$196.394	$196.39	$196.40	$196.40
Purchase #4	$106.73	6.398%	$113.5586	$113.56	$113.55	$113.60
Purchase #5	$140.70	8.274%	$152.3415	$152.34	$152.35	$152.30
Purchase #6	$196.55	7.356%	$211.0082	$211.01	$211.00	$211.00
Purchase #7	$80.44	6.234%	$85.4546	$85.45	$85.45	$85.50
7 purchase totals =	$868.02		$933.9507	$933.94	$933.90	$934.00