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	$179.71	5.365%	$189.3514	$189.35	$189.35	$189.40
Purchase #2	$168.31	5.670%	$177.8532	$177.85	$177.85	$177.90
Purchase #3	$182.89	3.836%	$189.9057	$189.91	$189.90	$189.90
Purchase #4	$242.35	5.677%	$256.1082	$256.11	$256.10	$256.10
Purchase #5	$32.34	4.874%	$33.9163	$33.92	$33.90	$33.90
Purchase #6	$214.61	3.462%	$222.0398	$222.04	$222.05	$222.00
Purchase #7	$228.60	7.491%	$245.7244	$245.72	$245.70	$245.70
7 purchase totals =	$1,248.81		$1,314.8990	$1,314.90	$1,314.85	$1,314.90