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	$139.73	3.582%	$144.7351	$144.74	$144.75	$144.70
Purchase #2	$71.25	3.193%	$73.525	$73.53	$73.55	$73.50
Purchase #3	$140.90	11.278%	$156.7907	$156.79	$156.80	$156.80
Purchase #4	$230.59	8.706%	$250.6652	$250.67	$250.65	$250.70
Purchase #5	$163.92	3.380%	$169.4605	$169.46	$169.45	$169.50
Purchase #6	$72.72	4.697%	$76.1357	$76.14	$76.15	$76.10
Purchase #7	$83.70	6.864%	$89.4452	$89.45	$89.45	$89.40
7 purchase totals =	$902.81		$960.7574	$960.78	$960.80	$960.70