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	$134.41	4.206%	$140.0633	$140.06	$140.05	$140.10
Purchase #2	$123.42	11.215%	$137.2616	$137.26	$137.25	$137.30
Purchase #3	$148.32	5.574%	$156.5874	$156.59	$156.60	$156.60
Purchase #4	$218.59	9.286%	$238.8883	$238.89	$238.90	$238.90
Purchase #5	$209.31	4.277%	$218.2622	$218.26	$218.25	$218.30
Purchase #6	$206.52	4.194%	$215.1814	$215.18	$215.20	$215.20
Purchase #7	$153.53	7.832%	$165.5545	$165.55	$165.55	$165.60
7 purchase totals =	$1,194.10		$1,271.7987	$1,271.79	$1,271.80	$1,272.00