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	$65.90	10.154%	$72.5915	$72.59	$72.60	$72.60
Purchase #2	$216.96	5.696%	$229.318	$229.32	$229.30	$229.30
Purchase #3	$190.78	8.198%	$206.4201	$206.42	$206.40	$206.40
Purchase #4	$120.97	13.295%	$137.053	$137.05	$137.05	$137.10
Purchase #5	$169.99	5.338%	$179.0641	$179.06	$179.05	$179.10
Purchase #6	$136.31	4.645%	$142.6416	$142.64	$142.65	$142.60
Purchase #7	$206.79	3.208%	$213.4238	$213.42	$213.40	$213.40
7 purchase totals =	$1,107.70		$1,180.5121	$1,180.50	$1,180.45	$1,180.50