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	$163.27	5.862%	$172.8409	$172.84	$172.85	$172.80
Purchase #2	$228.62	13.866%	$260.3204	$260.32	$260.30	$260.30
Purchase #3	$191.59	4.605%	$200.4127	$200.41	$200.40	$200.40
Purchase #4	$245.28	11.470%	$273.4136	$273.41	$273.40	$273.40
Purchase #5	$52.33	4.804%	$54.8439	$54.84	$54.85	$54.80
Purchase #6	$213.38	5.654%	$225.4445	$225.44	$225.45	$225.40
Purchase #7	$48.94	5.446%	$51.6053	$51.61	$51.60	$51.60
7 purchase totals =	$1,143.41		$1,238.8813	$1,238.87	$1,238.85	$1,238.70