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	$120.65	9.633%	$132.2722	$132.27	$132.25	$132.30
Purchase #2	$136.97	4.129%	$142.6255	$142.63	$142.65	$142.60
Purchase #3	$174.58	8.701%	$189.7702	$189.77	$189.75	$189.80
Purchase #4	$38.91	10.229%	$42.8901	$42.89	$42.90	$42.90
Purchase #5	$94.77	5.661%	$100.1349	$100.13	$100.15	$100.10
Purchase #6	$113.60	5.331%	$119.656	$119.66	$119.65	$119.70
Purchase #7	$222.55	7.126%	$238.4089	$238.41	$238.40	$238.40
7 purchase totals =	$902.03		$965.7578	$965.76	$965.75	$965.80