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	$135.84	13.653%	$154.3862	$154.39	$154.40	$154.40
Purchase #2	$90.95	7.781%	$98.0268	$98.03	$98.05	$98.00
Purchase #3	$164.62	11.184%	$183.0311	$183.03	$183.05	$183.00
Purchase #4	$145.84	8.427%	$158.1299	$158.13	$158.15	$158.10
Purchase #5	$105.72	6.260%	$112.3381	$112.34	$112.35	$112.30
Purchase #6	$52.32	13.504%	$59.3853	$59.39	$59.40	$59.40
Purchase #7	$183.32	11.223%	$203.894	$203.89	$203.90	$203.90
7 purchase totals =	$878.61		$969.1914	$969.20	$969.30	$969.10