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	$117.33	13.350%	$132.9936	$132.99	$133.00	$133.00
Purchase #2	$142.56	6.795%	$152.247	$152.25	$152.25	$152.20
Purchase #3	$68.48	4.305%	$71.4281	$71.43	$71.45	$71.40
Purchase #4	$77.87	7.703%	$83.8683	$83.87	$83.85	$83.90
Purchase #5	$244.48	13.866%	$278.3796	$278.38	$278.40	$278.40
Purchase #6	$98.95	5.106%	$104.0024	$104.00	$104.00	$104.00
Purchase #7	$211.58	12.804%	$238.6707	$238.67	$238.65	$238.70
7 purchase totals =	$961.25		$1,061.5897	$1,061.59	$1,061.60	$1,061.60