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	$212.35	7.709%	$228.7201	$228.72	$228.70	$228.70
Purchase #2	$152.25	8.571%	$165.2993	$165.30	$165.30	$165.30
Purchase #3	$186.66	5.309%	$196.5698	$196.57	$196.55	$196.60
Purchase #4	$11.86	12.752%	$13.3724	$13.37	$13.35	$13.40
Purchase #5	$83.42	5.854%	$88.3034	$88.30	$88.30	$88.30
Purchase #6	$198.94	13.345%	$225.4885	$225.49	$225.50	$225.50
Purchase #7	$13.42	4.743%	$14.0565	$14.06	$14.05	$14.10
7 purchase totals =	$858.90		$931.8100	$931.81	$931.75	$931.90