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	$156.84	6.608%	$167.204	$167.20	$167.20	$167.20
Purchase #2	$234.81	9.403%	$256.8892	$256.89	$256.90	$256.90
Purchase #3	$149.56	4.513%	$156.3096	$156.31	$156.30	$156.30
Purchase #4	$42.55	3.261%	$43.9376	$43.94	$43.95	$43.90
Purchase #5	$187.28	8.601%	$203.388	$203.39	$203.40	$203.40
Purchase #6	$50.43	5.798%	$53.3539	$53.35	$53.35	$53.40
Purchase #7	$171.59	10.463%	$189.5435	$189.54	$189.55	$189.50
7 purchase totals =	$993.06		$1,070.6258	$1,070.62	$1,070.65	$1,070.60