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	$212.25	11.806%	$237.3082	$237.31	$237.30	$237.30
Purchase #2	$19.63	11.533%	$21.8939	$21.89	$21.90	$21.90
Purchase #3	$220.76	4.493%	$230.6787	$230.68	$230.70	$230.70
Purchase #4	$38.95	11.421%	$43.3985	$43.40	$43.40	$43.40
Purchase #5	$188.26	4.269%	$196.2968	$196.30	$196.30	$196.30
Purchase #6	$93.29	7.833%	$100.5974	$100.60	$100.60	$100.60
Purchase #7	$240.87	8.492%	$261.3247	$261.32	$261.30	$261.30
7 purchase totals =	$1,014.01		$1,091.4982	$1,091.50	$1,091.50	$1,091.50