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	$134.58	9.128%	$146.8645	$146.86	$146.85	$146.90
Purchase #2	$229.27	4.727%	$240.1076	$240.11	$240.10	$240.10
Purchase #3	$131.43	12.743%	$148.1781	$148.18	$148.20	$148.20
Purchase #4	$133.55	6.629%	$142.403	$142.40	$142.40	$142.40
Purchase #5	$243.59	3.425%	$251.933	$251.93	$251.95	$251.90
Purchase #6	$117.55	8.173%	$127.1574	$127.16	$127.15	$127.20
Purchase #7	$186.46	10.137%	$205.3615	$205.36	$205.35	$205.40
7 purchase totals =	$1,176.43		$1,262.0051	$1,262.00	$1,262.00	$1,262.10