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	$70.71	10.501%	$78.1353	$78.14	$78.15	$78.10
Purchase #2	$127.85	4.491%	$133.5917	$133.59	$133.60	$133.60
Purchase #3	$156.51	3.320%	$161.7061	$161.71	$161.70	$161.70
Purchase #4	$188.48	9.305%	$206.0181	$206.02	$206.00	$206.00
Purchase #5	$95.75	9.137%	$104.4987	$104.50	$104.50	$104.50
Purchase #6	$231.36	7.735%	$249.2557	$249.26	$249.25	$249.30
Purchase #7	$240.85	9.148%	$262.883	$262.88	$262.90	$262.90
7 purchase totals =	$1,111.51		$1,196.0886	$1,196.10	$1,196.10	$1,196.10