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	$32.98	7.731%	$35.5297	$35.53	$35.55	$35.50
Purchase #2	$183.38	11.528%	$204.52	$204.52	$204.50	$204.50
Purchase #3	$78.57	3.632%	$81.4237	$81.42	$81.40	$81.40
Purchase #4	$115.25	13.719%	$131.0611	$131.06	$131.05	$131.10
Purchase #5	$179.87	7.750%	$193.8099	$193.81	$193.80	$193.80
Purchase #6	$167.77	11.683%	$187.3706	$187.37	$187.35	$187.40
Purchase #7	$186.49	5.210%	$196.2061	$196.21	$196.20	$196.20
7 purchase totals =	$944.31		$1,029.9211	$1,029.92	$1,029.85	$1,029.90