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	$215.80	3.146%	$222.5891	$222.59	$222.60	$222.60
Purchase #2	$107.37	11.641%	$119.8689	$119.87	$119.85	$119.90
Purchase #3	$228.86	12.701%	$257.9275	$257.93	$257.95	$257.90
Purchase #4	$148.80	9.445%	$162.8542	$162.85	$162.85	$162.90
Purchase #5	$156.62	7.438%	$168.2694	$168.27	$168.25	$168.30
Purchase #6	$104.54	12.240%	$117.3357	$117.34	$117.35	$117.30
Purchase #7	$158.87	3.744%	$164.8181	$164.82	$164.80	$164.80
7 purchase totals =	$1,120.86		$1,213.6629	$1,213.67	$1,213.65	$1,213.70