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	$222.53	9.390%	$243.4256	$243.43	$243.45	$243.40
Purchase #2	$137.30	6.406%	$146.0954	$146.10	$146.10	$146.10
Purchase #3	$48.27	6.647%	$51.4785	$51.48	$51.50	$51.50
Purchase #4	$212.98	7.488%	$228.9279	$228.93	$228.95	$228.90
Purchase #5	$78.68	10.240%	$86.7368	$86.74	$86.75	$86.70
Purchase #6	$187.83	4.485%	$196.2542	$196.25	$196.25	$196.30
Purchase #7	$39.27	11.206%	$43.6706	$43.67	$43.65	$43.70
7 purchase totals =	$926.86		$996.5890	$996.60	$996.65	$996.60