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	$206.70	8.312%	$223.8809	$223.88	$223.90	$223.90
Purchase #2	$41.44	10.801%	$45.9159	$45.92	$45.90	$45.90
Purchase #3	$78.26	5.328%	$82.4297	$82.43	$82.45	$82.40
Purchase #4	$201.94	10.475%	$223.0932	$223.09	$223.10	$223.10
Purchase #5	$87.93	13.458%	$99.7636	$99.76	$99.75	$99.80
Purchase #6	$177.91	8.516%	$193.0608	$193.06	$193.05	$193.10
Purchase #7	$215.40	6.556%	$229.5216	$229.52	$229.50	$229.50
7 purchase totals =	$1,009.58		$1,097.6657	$1,097.66	$1,097.65	$1,097.70