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	$176.71	4.280%	$184.2732	$184.27	$184.25	$184.30
Purchase #2	$165.73	6.666%	$176.7776	$176.78	$176.80	$176.80
Purchase #3	$119.49	3.425%	$123.5825	$123.58	$123.60	$123.60
Purchase #4	$150.70	9.439%	$164.9246	$164.92	$164.90	$164.90
Purchase #5	$69.37	4.187%	$72.2745	$72.27	$72.25	$72.30
Purchase #6	$13.75	3.763%	$14.2674	$14.27	$14.25	$14.30
Purchase #7	$120.37	8.226%	$130.2716	$130.27	$130.25	$130.30
7 purchase totals =	$816.12		$866.3714	$866.36	$866.30	$866.50