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	$30.60	4.411%	$31.9498	$31.95	$31.95	$31.90
Purchase #2	$104.53	12.263%	$117.3485	$117.35	$117.35	$117.30
Purchase #3	$162.51	8.850%	$176.8921	$176.89	$176.90	$176.90
Purchase #4	$171.63	9.320%	$187.6259	$187.63	$187.65	$187.60
Purchase #5	$161.25	10.309%	$177.8733	$177.87	$177.85	$177.90
Purchase #6	$47.32	13.813%	$53.8563	$53.86	$53.85	$53.90
Purchase #7	$234.88	12.424%	$264.0615	$264.06	$264.05	$264.10
7 purchase totals =	$912.72		$1,009.6074	$1,009.61	$1,009.60	$1,009.60