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	$213.58	11.473%	$238.084	$238.08	$238.10	$238.10
Purchase #2	$196.39	9.499%	$215.0451	$215.05	$215.05	$215.00
Purchase #3	$40.72	3.298%	$42.0629	$42.06	$42.05	$42.10
Purchase #4	$171.67	4.730%	$179.79	$179.79	$179.80	$179.80
Purchase #5	$12.42	6.532%	$13.2313	$13.23	$13.25	$13.20
Purchase #6	$195.40	13.661%	$222.0936	$222.09	$222.10	$222.10
Purchase #7	$246.74	10.586%	$272.8599	$272.86	$272.85	$272.90
7 purchase totals =	$1,076.92		$1,183.1668	$1,183.16	$1,183.20	$1,183.20