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	$161.69	13.233%	$183.0864	$183.09	$183.10	$183.10
Purchase #2	$87.35	13.804%	$99.4078	$99.41	$99.40	$99.40
Purchase #3	$12.85	3.223%	$13.2642	$13.26	$13.25	$13.30
Purchase #4	$73.67	9.565%	$80.7165	$80.72	$80.70	$80.70
Purchase #5	$84.32	5.715%	$89.1389	$89.14	$89.15	$89.10
Purchase #6	$176.70	11.402%	$196.8473	$196.85	$196.85	$196.80
Purchase #7	$247.32	5.770%	$261.5904	$261.59	$261.60	$261.60
7 purchase totals =	$843.90		$924.0515	$924.06	$924.05	$924.00