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	$129.64	11.655%	$144.7495	$144.75	$144.75	$144.70
Purchase #2	$166.58	5.703%	$176.0801	$176.08	$176.10	$176.10
Purchase #3	$223.97	5.425%	$236.1204	$236.12	$236.10	$236.10
Purchase #4	$78.41	4.585%	$82.0051	$82.01	$82.00	$82.00
Purchase #5	$95.78	7.412%	$102.8792	$102.88	$102.90	$102.90
Purchase #6	$71.28	10.417%	$78.7052	$78.71	$78.70	$78.70
Purchase #7	$76.72	4.162%	$79.9131	$79.91	$79.90	$79.90
7 purchase totals =	$842.38		$900.4526	$900.46	$900.45	$900.40