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	$163.71	8.349%	$177.3781	$177.38	$177.40	$177.40
Purchase #2	$158.89	13.826%	$180.8581	$180.86	$180.85	$180.90
Purchase #3	$45.88	4.324%	$47.8639	$47.86	$47.85	$47.90
Purchase #4	$82.37	6.715%	$87.9011	$87.90	$87.90	$87.90
Purchase #5	$240.59	10.281%	$265.3251	$265.33	$265.35	$265.30
Purchase #6	$96.34	3.783%	$99.9845	$99.98	$100.00	$100.00
Purchase #7	$55.34	7.767%	$59.6383	$59.64	$59.65	$59.60
7 purchase totals =	$843.12		$918.9491	$918.95	$919.00	$919.00