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	$55.88	9.567%	$61.226	$61.23	$61.25	$61.20
Purchase #2	$134.64	4.653%	$140.9048	$140.90	$140.90	$140.90
Purchase #3	$23.61	9.660%	$25.8907	$25.89	$25.90	$25.90
Purchase #4	$138.42	11.859%	$154.8352	$154.84	$154.85	$154.80
Purchase #5	$198.91	8.426%	$215.6702	$215.67	$215.65	$215.70
Purchase #6	$222.47	10.237%	$245.2443	$245.24	$245.25	$245.20
Purchase #7	$158.64	8.382%	$171.9372	$171.94	$171.95	$171.90
7 purchase totals =	$932.57		$1,015.7084	$1,015.71	$1,015.75	$1,015.60