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	$66.31	6.330%	$70.5074	$70.51	$70.50	$70.50
Purchase #2	$236.58	4.382%	$246.9469	$246.95	$246.95	$246.90
Purchase #3	$96.78	11.654%	$108.0587	$108.06	$108.05	$108.10
Purchase #4	$169.46	7.768%	$182.6237	$182.62	$182.60	$182.60
Purchase #5	$14.29	9.688%	$15.6744	$15.67	$15.65	$15.70
Purchase #6	$245.27	8.158%	$265.2791	$265.28	$265.30	$265.30
Purchase #7	$109.27	3.807%	$113.4299	$113.43	$113.45	$113.40
7 purchase totals =	$937.96		$1,002.5201	$1,002.52	$1,002.50	$1,002.50