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	$12.85	5.731%	$13.5864	$13.59	$13.60	$13.60
Purchase #2	$141.58	3.164%	$146.0596	$146.06	$146.05	$146.10
Purchase #3	$190.56	10.660%	$210.8737	$210.87	$210.85	$210.90
Purchase #4	$135.51	9.236%	$148.0257	$148.03	$148.05	$148.00
Purchase #5	$53.53	11.328%	$59.5939	$59.59	$59.60	$59.60
Purchase #6	$160.73	5.675%	$169.8514	$169.85	$169.85	$169.90
Purchase #7	$250.67	4.549%	$262.073	$262.07	$262.05	$262.10
7 purchase totals =	$945.43		$1,010.0637	$1,010.06	$1,010.05	$1,010.20