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	$103.82	9.721%	$113.9123	$113.91	$113.90	$113.90
Purchase #2	$85.59	8.520%	$92.8823	$92.88	$92.90	$92.90
Purchase #3	$245.74	7.284%	$263.6397	$263.64	$263.65	$263.60
Purchase #4	$177.77	10.269%	$196.0252	$196.03	$196.05	$196.00
Purchase #5	$237.80	10.803%	$263.4895	$263.49	$263.50	$263.50
Purchase #6	$74.65	3.271%	$77.0918	$77.09	$77.10	$77.10
Purchase #7	$61.56	9.838%	$67.6163	$67.62	$67.60	$67.60
7 purchase totals =	$986.93		$1,074.6571	$1,074.66	$1,074.70	$1,074.60