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	$158.43	3.702%	$164.2951	$164.30	$164.30	$164.30
Purchase #2	$171.25	9.358%	$187.2756	$187.28	$187.30	$187.30
Purchase #3	$141.88	12.720%	$159.9271	$159.93	$159.95	$159.90
Purchase #4	$86.45	3.407%	$89.3954	$89.40	$89.40	$89.40
Purchase #5	$150.40	12.266%	$168.8481	$168.85	$168.85	$168.80
Purchase #6	$110.67	4.626%	$115.7896	$115.79	$115.80	$115.80
Purchase #7	$177.50	10.781%	$196.6363	$196.64	$196.65	$196.60
7 purchase totals =	$996.58		$1,082.1672	$1,082.19	$1,082.25	$1,082.10