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	$119.31	10.193%	$131.4713	$131.47	$131.45	$131.50
Purchase #2	$62.84	13.736%	$71.4717	$71.47	$71.45	$71.50
Purchase #3	$176.68	11.199%	$196.4664	$196.47	$196.45	$196.50
Purchase #4	$78.44	11.870%	$87.7508	$87.75	$87.75	$87.80
Purchase #5	$181.97	6.595%	$193.9709	$193.97	$193.95	$194.00
Purchase #6	$77.52	3.760%	$80.4348	$80.43	$80.45	$80.40
Purchase #7	$148.71	10.789%	$164.7543	$164.75	$164.75	$164.80
7 purchase totals =	$845.47		$926.3202	$926.31	$926.25	$926.50