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	$194.79	3.438%	$201.4869	$201.49	$201.50	$201.50
Purchase #2	$39.52	10.159%	$43.5348	$43.53	$43.55	$43.50
Purchase #3	$13.92	12.364%	$15.6411	$15.64	$15.65	$15.60
Purchase #4	$30.55	9.604%	$33.484	$33.48	$33.50	$33.50
Purchase #5	$78.67	13.862%	$89.5752	$89.58	$89.60	$89.60
Purchase #6	$171.39	9.175%	$187.115	$187.12	$187.10	$187.10
Purchase #7	$59.55	6.171%	$63.2248	$63.22	$63.20	$63.20
7 purchase totals =	$588.39		$634.0618	$634.06	$634.10	$634.00