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	$43.68	7.777%	$47.077	$47.08	$47.10	$47.10
Purchase #2	$205.69	3.518%	$212.9262	$212.93	$212.95	$212.90
Purchase #3	$248.79	11.157%	$276.5475	$276.55	$276.55	$276.50
Purchase #4	$200.25	3.498%	$207.2547	$207.25	$207.25	$207.30
Purchase #5	$118.92	10.271%	$131.1343	$131.13	$131.15	$131.10
Purchase #6	$69.73	13.148%	$78.8981	$78.90	$78.90	$78.90
Purchase #7	$72.32	8.202%	$78.2517	$78.25	$78.25	$78.30
7 purchase totals =	$959.38		$1,032.0895	$1,032.09	$1,032.15	$1,032.10