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	$77.89	13.679%	$88.5446	$88.54	$88.55	$88.50
Purchase #2	$190.46	9.512%	$208.5766	$208.58	$208.60	$208.60
Purchase #3	$166.41	12.687%	$187.5224	$187.52	$187.50	$187.50
Purchase #4	$173.81	9.676%	$190.6279	$190.63	$190.65	$190.60
Purchase #5	$180.95	7.706%	$194.894	$194.89	$194.90	$194.90
Purchase #6	$63.64	7.147%	$68.1884	$68.19	$68.20	$68.20
Purchase #7	$250.29	3.157%	$258.1917	$258.19	$258.20	$258.20
7 purchase totals =	$1,103.45		$1,196.5456	$1,196.54	$1,196.60	$1,196.50