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	$184.33	6.509%	$196.328	$196.33	$196.35	$196.30
Purchase #2	$134.94	3.525%	$139.6966	$139.70	$139.70	$139.70
Purchase #3	$243.94	11.401%	$271.7516	$271.75	$271.75	$271.80
Purchase #4	$236.76	12.478%	$266.3029	$266.30	$266.30	$266.30
Purchase #5	$209.60	10.427%	$231.455	$231.46	$231.45	$231.50
Purchase #6	$191.64	13.796%	$218.0787	$218.08	$218.10	$218.10
Purchase #7	$158.39	6.315%	$168.3923	$168.39	$168.40	$168.40
7 purchase totals =	$1,359.60		$1,492.0051	$1,492.01	$1,492.05	$1,492.10